US staff at the Organization for Security and Cooperation in Europe (OSCE) started to withdraw by car from the rebel-held city of Donetsk in eastern Ukraine on Sunday, a Reuters witness said, amid fears of a possible Russian invasion.
The United States and its allies have urged their citizens to leave Ukraine right away to avoid an invasion, including a possible air assault, warning an attack could occur at any time.
Russia has accused Western nations of spreading lies.
Earlier on Saturday, US Secretary of State Antony Blinken said the risk of Russian military action in Ukraine is high and imminent enough to justify the departure of much of the staff at US embassy in Kyiv, which the State
Department announced earlier.
"We ordered the departure of most of the Americans still at the US embassy in Kyiv. The risk of Russian military action is high enough and the threat is imminent enough that this is the prudent thing to do," Blinken told a news conference in Honolulu.
This added to the State Department's call earlier this week for private US citizens to leave Ukraine immediately.