Soviet Landing at Shumshu (from Russian Wikipedia)

At 0238 on August 18, the coastal Soviet battery from Cape Lopatka on
the Kamchatka coast opened fire and fired until 0450. At 0422 the
landing of the advanced naval landing detachment began (a marine
battalion minus one company), machine gun and mortar companies, machine
gun and anti-tank rifle companies, combat engineer company, chemical
reconnaissance platoon, foot reconnaissance platoon) under the command
of the deputy commander of the 138th Infantry Regiment Major Shutov.
There were 1363 people in the advance detachment. Insufficient
reconnaissance was revealed immediately - the bottom in the landing
area turned out to have large pitfalls, and the approach of the craft
close to the shore was difficult. Overloaded landing craft stopped far
from the shore and heavily-armed troops were forced to partially swim
to the shore through the ocean surf. Some drowned.
It was an hour later before the Japanese discovered the landing and
opened fire on the landing ships carrying units of the 1st echelon
(138th Infantry Regiment). Just how unexpected the landing was for the
Japanese can be judged by the fact that their advanced trenches were
not occupied, and the major detachment of Major Shutov, taking the
Japanese by surprise, advanced forward up to 2km without much
resistance.
The enemy, having discovered the landing, opened strong artillery fire
from batteries located on the capes of Kokutan-Saki and Kotomari-Saki
and the tanker Mariupol (a Soviet vessel stranded off the island of
Shumshu even before the outbreak of hostilities and turned into a
battery by the Japanese).
By 0900 on August 18, the landing of the first echelon of the main
landing forces was completed (138th rifle regiment -- 3 artillery
divisions were included, including anti-tank divisions, but only four
45mm guns were initially landed plus a company of anti-tank rifles). They successfully seized two dominant heights looming over the landing zone.
However from 1100-1200 hours the resistance of the Japanese increased
sharply. Powerful Japanese counterattacks were launched with the
support of tanks. The battle became very fierce, reaching melee . Many
positions and hills several times passed from the Japanese to the
Soviet units and vice versa, then the deeds of the foreman of the 1st
article N. A. Vilkov and Red Navy P. I. Ilyichev , covering the
embrasures of the Japanese bunkers, were accomplished. In this battle,
both sides suffered most of their casualties. The Japanese rushed
reinforcing units onto Shumsha from nearby Paramushir. The landing
difficulties were compounded by the failure of 21 of the 22 radio
stations, which sometimes lost control of the battle from the Soviet
command.
In the afternoon the Japanese launched decisive attacks, throwing
tanks from a tank regiment at them. With great losses they advanced
but could not push the landing back into the sea. The bulk of the
tanks were destroyed by grenades and anti-tank rifle fire. Of the 60
tanks, up to 40 were destroyed or damaged (the Japanese recognized the
loss of only 27 tanks), in this battle the commander of the tank
regiment died. But it came at a high price - about 200 troops were
lost dead.
Japanese guns began firing heavily on ships approaching the shore with
the following landing units and inflicted significant losses on Soviet
ships... The crews of the landing craft had heavy losses. The ships
also attacked Japanese aircraft, but without significant success...2
aircraft were shot down by anti-aircraft fire of our ships.
Under Japanese fire, Soviet ships nonetheless landed troops of the
main landing forces. The impossibility of reinforcing the landing with
artillery had an extremely adverse effect on the course of the battle
- initially there were no watercraft for unloading guns from ships and delivering them to shore. The Japanese command also hastily
transferred reinforcements from Paramushira to Shumsha.
At 1800, the landing units launched a decisive attack on the dominant
height of 171 with the support of the fire of all ship guns. The
battle again took on an extremely cruel character, three fighters
broke into Japanese positions and twice the Japanese pushed them out
of there in counterattacks. The battle was full of hand-to-hand
combat. Nevertheless, by 2000 the Soviet units finally threw back the
Japanese troops and tightly secured it.
The second echelon of the landing - the 373rd rifle regiment - landed
in the evening. Also at night, a temporary pier was built to receive
new ships with guns and ammunition, finally managing to bring ashore
11 guns, with plentiful ammunition and explosives.
The Japanese forces on Shumshu opposing the invasion are described:
The northernmost island of the archipelago, Shumshu, located just 6.5
miles (about 12 kilometers) from the southern coast of Kamchatka, was
fortified. The 73rd Infantry Brigade of the 91st Infantry Division,
the 31st Air Defense Regiment, the Fortress Artillery Regiment, the
11th Tank Regiment (without one company), the garrison of the Kataoka
Naval Base, the airdrome team, and 2 Marine Corps (ricocentai) were
stationed there, 51st (942 people) and 52nd (333 people) with 16 Ka-Mi
tanks, two separate mortar battalions, the 18th and 19th, armed with
heavy rocket launchers, separate units. The depth of the engineering
structures of the anti-invasion defense was 3-4 km, on the island
there were 34 concrete artillery bunkers and 24 bunkers, 310 closed
machine gun points, numerous underground shelters for troops and
military equipment up to 50 meters deep. The fortifications were
connected by means of communications into a single defensive system.
The Shumshu garrison was 8500 people, over 100 guns of all systems,
and 80 tanks.
The page quoted above "Capture of Shumshu" gives a total of 80 Japanese tanks, from 11th Tank Regiment (64 tanks) and Marine forces (16 tanks). The other page does not include the Marines at all in the Japanese force listing and gives a total of just 60 tanks. Both pages agree that 60 tanks attacked the beach-head, with the second page claiming "all" the Japanese tanks were committed, and both pages agree that around 40 tanks were destroyed (and that the Japanese claimed it was only 27).
First-hand Soviet account of the landing on Shumshu
From the memoirs of Ivan Alekseevich Bezdelov, a fighter of the 138th Infantry Regiment of the 101st Mountain Rifle Division:
August 18, 1945 in the morning at dawn, the landing began. I landed
with the second battalion, which was on the 324th self-propelled
barge. When approaching the shore, the gangway was thrown, but during
this period the Japanese disabled the motor, and the barge went back
from the push of the gangway into the ground, while the sailors
dropped anchor, the barge went 60-70 meters from the shore, which
complicated the landing, but despite on this, the battalion landed
with great losses.
The battalion commander, Captain Lapatin (or Lapshin, I don’t remember
his last name) was killed immediately on deck by an armor-piercing
shell. Our group advanced to the left of the height in order to cross
the road going from Nagasaki (the southern part of the island) to a
height named 101, which was strengthened by the Japanese and was
considered an impregnable fortress. This height was connected by
underground passages to the next height, and further underground
passages went directly to the seashore.
Despite the inaccessibility of the heights, the soldiers took it. The
soldiers, sergeants and officers showed massive heroism, there the
Komsomol soldiers Novikov Vasily, Astudin Grisha, Trufanov Misha died,
but you can’t count all of them. Captain Savushkin, a member of the
CPSU, commander of an assault rifle company, who was in the capture
group, was awarded the title of Hero of the Soviet Union for his
heroism, stamina and courage (posthumously) ...
Our squad ... attacked with the left wing with the task of cutting the
road from Nagasaki to the height 101, along which reinforcements and
Japanese tanks were thrown. The Japanese tanks did not reach their
destination, since the first tank was hit from an anti-tank rifle by a
member of the 138 Komsomol member of the SP (I could not remember the
name).
Japanese mortars from a height saw our squad, we were in full view. In
addition, our artillery opened fire from the ship, and the shells
began to burst at our location, we were under crossfire ... But we
still completed our combat mission and moved forward.
Soviet troops landing on Shimshu.
Soviet Press Report
Here is how the Kamchatskaya Pravda newspaper wrote about this fight in August 1945:
“Motherland, dear comrade Stalin! We are going into battle in the name
of our victory and the happiness of our people. In battle, we will not
shame the glory of Russian weapons and will fulfill our military duty
to the end. We will give all our strength, and if necessary, our life
for the benefit of our beloved Motherland. ”
And then the moment came when the words of the oath were to be
realized.
Junior Sergeant Stepan Ryndin was the first to approach the lead tank
and throw a bunch of grenades at it. The carousel spun in one place.
But Ryndin himself was seriously injured. Overcoming the excruciating
pain, he boldly went to the tank to kill him with the last grenade. At
the tank itself, the brave sailor was hit by a burst of enemy machine
guns.
Several tanks rushed forward. Other sailors stood in their way. They
fearlessly entered into combat with armored vehicles. Having tied up
with grenades, with exclamations: “For the Motherland!”, “For Stalin!”
- some rushed under the tracks, others shot point-blank tank crews through observation openings. Heroic death killed lieutenant
technician Alexander Vodynin and senior sergeant Ivan Kobzar. They
gave their lives for the benefit of their beloved Motherland, in the
name of victory over the enemy.
One by one, tanks were engulfed in flames. The air smelled of
stench-burn. After the first skirmishes with the sailors, the Japanese
tankers no longer dared to go on a frontal attack. They resorted to
intricate maneuvers, but nothing could save them anymore - death
overtook them everywhere.

Yet another revealing and fascinating perspective from a Russian blog:
The Last Tank Battle of WWII
Early in the morning of August 18, the Soviet advance detachment from
Kamchatka landed on Shumsha and, catching the Japanese by surprise,
advanced almost 2 kilometers without resistance. Thus began the Kuril
landing operation.
Unfortunately after this the landing was no longer so flawless. An
hour later ships with the first echelon of landing approached the
landing site. The now roused Japanese opened up a hurricane of fire.
The situation was aggravated by the fact that overloaded ships at low
tide could not come close to the shore. A detachment of fishing
kungasas (Far Eastern boats), which were intended to be used to
deliver soldiers to the shore, lost orientation in the fog and did not
arrive on time. The landing forces had to land directly into the water
and swim to the shore. Water damaged their radios, so that
communication with the ships was established only by 11 o’clock in the
morning, virtually no artillery could be unloaded, and the most
tragic: it was at this moment that most of the troops later recorded
as "missing" died.
The Japanese themselves, however, also for quite some time could not
understand what was happening and who was attacking them. Panicked
reports of thousands of Americans landing flew from the island to
headquarters. Only a few hours later did the Japanese realize that
they were being attacked by the Russians. Ignorance of the strength
and nationality of the enemy did not prevent the commander of the
Shumshu garrison from giving the order "to push the troops into the
sea."
The first of the Japanese armored vehicles to the landing site were
light tanks. At about 3:30, Colonel Ikeda sent a reconnaissance tank
company to Captain Ito Isao - 11 "Ha-Go" light tanks. By the standards
of 1945, the vehicles were hopelessly outdated. But in conditions when
most of the landing artillery still remained on the ships, even they
posed a very serious threat.
The landing forces were covered with fire from the sea by a patrol
boat. But the main role in repelling the Japanese attack was played by
the heroism of the Kamchatka marines. In award documents for Shumshu,
the phrase “threw himself under an enemy tank with grenades” is found
repeatedly. Having lost six or seven vehicles, the Japanese were still
able to push the landing forces to the eastern slope of height 171
(Severnaya Mountain on modern maps). There, Soviet units began to dig
in hastily, partially adapting captured Japanese positions for
defense.
The description of further hostilities between the Soviet and Japanese
sides now diverges, quite strongly in places.
According to the Japanese version, a second tank company came to the
aid of their reconnaissance group, but this was not enough. As a
result, the Japanese lost many tanks, and Colonel Ikeda himself died
in the battle.
According to the Soviet version, the commander of the second landing
echelon, Colonel Artyushin, having received a report on available
Japanese reserves, put forward most of his anti-tank weapons - the
total of anti-tank rifles (PTR), grenade launchers and several 45mm
guns brought ashore. At about 14:00 Kamchatka time, the Japanese
launched an attack with 18 tanks. Almost all of them were stopped on
our line of defense, knocked out by concentrated PTR fire. Only one
Japanese tank could get out of the battle.

A very detailed description of the fighting around the landing zone can be found here in another excellent Russian blog -- in Russian and unfortunately too long to be included in full here -- but it does support the much lower tank numbers presented in the quoted blog above, and the two-phased nature of the Japanese tank attack as described. It appears the 11th Tank Regiment was dispersed around the island and only about half was able to reach the battle before negotiations began.

Sources:
Курильская десантная операция (Kuril Landing Operation - Russian Wikipedia)
Взятие Шумшу (Capture of Shumshu - Russian Wikipedia)
Russian 70th Anniversary tribute to the battle
Последний танковый бой Второй мировой войны (The Last Tank Battle of WWII)
Десантники против танков: бой на острове Шумшу
Primary source used extensively in the Russian Wikipedia articles:
Описание Курильской десантной операции
(Description of the Kuril landing operation. Headquarters of the Far Eastern Military District. Yuzhno-Sakhalinsk, 1947 / OBD "Memory of the people")
--- many other sources are listed.