That's right. After 6 months of war between Ukraine and Russia, the U.S. Embassy is now alarmed by the prospect of a possible Russian air assault on Kiev, Lviv and other large Ukrainian cities. Here is the "Security Alert":

Ukraine Event:The Department of State has information that Russia is stepping up efforts to launch strikes against Ukraine's civilian infrastructure and government facilities in the coming days. Russian strikes in Ukraine pose a continued threat to civilians and civilian infrastructure. The U.S. Embassy urges U.S. citizens to depart Ukraine now using privately available ground transportation options if it is safe to do so.

See additional safety information from a previous Security Alert below:

If you hear a loud explosion or if sirens are activated, immediately seek cover.