The US government is urging Americans in Ukraine to leave the country immediately

The US government is urging Americans in Ukraine to leave the country immediately, warning that Russia is stepping up efforts to launch attacks on civilian infrastructure and government facilities in the coming days.

"The US Embassy urges US citizens to depart Ukraine now using privately available ground transportation options if it is safe to do so," a security alert on the embassy's website said.
"The security situation throughout Ukraine is highly volatile and conditions may deteriorate without warning."