The U.S. Embassy in Moscow urged American citizens in Russia to think about leaving the country immediately, as some airlines halt flights there and some countries close their skies to Russian aircraft.

“U.S. citizens should consider departing Russia immediately via commercial options still available”, - the Embassy said in a statement on its website.

U.S. officials in recent weeks have urged Americans not to travel to Russia, and warned that the U.S. government could not help in any evacuation of Americans from there.

An earlier alert recommended Americans develop contingency plans about how to leave the country if necessary.