Ukrainian President Volodymyr Zelenskyy has warned of a ramped-up Russian offensive in his country's east,

with civilians rushing to flee the region ahead of what many fear could be a brutal new phase in the war.

Russia has deployed tens of thousands of troops to "prepare new attacks," Zelenskyy warned on Monday,

a day after he vowed his country's troops were prepared to "respond" to the fresh

assault Moscow's forces appeared poised to launch in eastern Ukraine.

Satellite images captured by Maxar, a commercial firm that works with the U.S. government,

appeared to show an 8-mile-long convoy of Russian military vehicles moving south

toward the Donbas area that seems likely to be the focus of a major new offensive.

It comes as Russia has appointed a general with a record of brutality in Syria to take over its operations in Ukraine,

a U.S. official and a Western official confirmed to NBC News.

Russia-Ukraine War News