Multiple air defense missile systems deployed by Russia on two disputed islands off northern Japan in 2020 have been moved off the isles, an analysis of satellite images showed Thursday, raising the possibility that Moscow is repurposing weapons from its Far East for use in the war against Ukraine.

Yu Koizumi, a lecturer at the University of Tokyo, made the analysis based on satellite images of the Etorofu and Kunashiri islands taken by U.S. space tech company Maxar Technologies Inc.

Koizumi said he is also convinced that old tanks and artillery previously stored at a military facility in Sakhalin are being sent to the frontlines in Ukraine.

File photo shows an S-300V4 surface-to-air missile system on the Chishima Islands, also known as the Kuril Islands, unveiled by Russia in 2020. (Photo courtesy of the Ministry of Defence of the Russian Federation)(Kyodo)

Missile units equipped with S-300V4 surface-to-air missile systems were stationed in Etorofu's Hitokappu Bay, known as Kasatka Bay in Russia, and near Kunashiri's central settlement of Furukamappu, known as Yuzhno-Kurilsk in Russia.

Multiple transporter erector launchers carrying S-300V4 missiles, radars, and other equipment were visible at both military stations between mid and late September last year.

Koizumi said it is possible they were redeployed to Russia's western region near its border with Ukraine in preparation for a potential attack.

He also speculates that a large number of old tanks and howitzers at a military facility in southern Sakhalin were sent to Ukraine after being temporarily taken to factories for repairs.

Troops from the Far East are also being dispatched to Ukraine. An elite naval infantry brigade based in Vladivostok has suffered significant losses in combat, and some residents of the Etorofu and Kunashiri islands have died after being mobilized, according to Koizumi.

"The Russian military is deploying all weapons at their disposal, which is evidence of their active engagement in the conflict," Koizumi said.

Etorofu and Kunashiri are among four disputed islands called and claimed as the Northern Territories by Japan and administered by Russia, which calls them the Southern Kurils.