Japan said Friday it will expel eight Russian diplomats and officials, calling Moscow's actions in Ukraine "categorically unacceptable" and a violation of international law.

The expulsions come after a wave of similar moves in Europe as Ukraine's allies pile pressure on Moscow following allegations of war crimes by its troops in areas around Kyiv.

"As a result of our country's comprehensive judgment, we have requested the expulsion of eight diplomats from the Russian Embassy in Japan and officials from the Office of the Trade Representative of the Russian Federation," Foreign Ministry spokesperson Hikariko Ono said.

She said Russia's Ambassador to Tokyo Mikhail Yurievich Galuzin had been informed of the decision in a meeting with Vice Foreign Minister Takeo Mori.

The ambassador was told that the killing of civilians "is a serious violation of international humanitarian law and a war crime," Ono said.

"It is categorically unacceptable and we strongly condemn this."

The expulsion does not affect Galuzin, officials said.

Japan has joined tough Western sanctions on Moscow over its invasion, including joining the G-7 in fresh measures on Thursday.