DONETSK, Ukraine (REUTERS) - Ukraine again flew its flag over the regional administration building in the eastern city of Donetsk on Thursday, and the police said pro-Moscow demonstrators who had seized it had left overnight.

"It was recommended that people leave the building. Everyone left," a police spokeswoman said.

Donetsk, home city of deposed President Viktor Yanukovich, has seen the most persistent pro-Moscow demonstrations in a wave of protests that erupted on Saturday hours before President Vladimir Putin declared Russia's right to invade.

Kiev says the protests in its eastern and southern cities were orchestrated by Moscow as justification for a possible assault.