Russia-Ukraine updates: US sanctions Russian military shipbuilder, diamond miner

The General Staff of the Ukrainian Armed Forces said Monday it is monitoring large movements of Russian troops and reinforcements in eastern Ukraine.

The General Staff said it expects Russian forces to launch a possibly major offensive in the Donbas region within the next 24 hours, particularly against the city of Severodonetsk, which is the administrative center of the government-controlled areas of the Luhansk Oblast.

Meanwhile, Donetsk Oblast Gov. Pavlo Kyrylenko has urged civilians to evacuate now, even from areas not close to the front lines.

Prior to Russia's invasion of Ukraine on Feb. 24, Russian President Vladimir Putin announced his recognition of two breakaway areas of eastern Ukraine's Donbas region that share a border with Russia -- the self-declared Donetsk and Luhansk people's republics. Russia-backed separatist forces have controlled these parts of Ukraine's Donetsk and Luhanks oblasts since 2014.

-ABC News' Yulia Drozd

Ukrainian President Volodymyr Zelenskyy visited on Monday the decimated city of Bucha, where Ukrainian officials have accused Russian troops of committing war crimes against civilians.

Zelenskyy toured the Kyiv suburb that was retaken by Ukrainian forces in recent days. Zelenskyy went to a road in the city littered with destroyed Russian equipment and he spoke to local residents.

Zelenskyy repeated accusations that Russia committed war crimes and genocide after Ukrainian officials said 410 people believed to have been civilians were found dead, many with their hands bound behind their backs and shot at close range.

Russian officials have denied the accusation and have requested the U.N. Security Council investigate.

Ukraine has accused a brigade of the Russian Ground Forces of committing war crimes in the Ukrainian city of Bucha, northwest of Kyiv.

The Main Directorate of Intelligence of the Ukrainian Ministry of Defense published online Monday what it said was a list with the names of hundreds of personnel of Russia's 64th Motor Rifle Brigade whom they believe were directly responsible for atrocities in Bucha. Ukrainian officials have said there is evidence of other Russian units being involved.

Ukrainian authorities announced Sunday that 410 civilians were found dead in recently recaptured towns near the capital as part of an investigation into possible war crimes by Russian forces. Images emerged showing bodies, some of which showed signs of torture, in civilian clothes strewn in streets and in mass graves across Bucha, northwest of Kyiv. ABC News journalists on the ground saw some of the dead, including a family that locals said were executed with their hands bound.

Russia has denied the claims.

-ABC News' Natalia Kushnir and Fidel Pavlenko

A $90 million yacht that belongs to Russian oligarch Viktor Vekselberg was seized Monday in Marina Real in the Spanish port of Palma de Mallorca, two U.S. law enforcement sources told ABC News.

The 255-foot yacht was seized by Spanish authorities and KleptoCapture, the U.S. Department of Justice task force charged with finding assets of oligarchs trying to evade sanctions over Russia’s invasion of Ukraine.

Vekselberg was among the oligarchs sanctioned previously by the United States in 2018 after Russia invaded Crimea.

The task force is trying to find yachts, airplanes and other moveable properties before the oligarchs can move them to jurisdictions where it might be more difficult for U.S. authorities to investigate.

"Today marks our taskforce’s first seizure of an asset belonging to a sanctioned individual with close ties to the Russian regime. It will not be the last," U.S. Attorney General Merrick Garland said in a statement. "Together, with our international partners, we will do everything possible to hold accountable any individual whose criminal acts enable the Russian government to continue its unjust war."

-ABC News' Luke Barr and Aaron Katersky