The U.S. Embassy in Russia issued a security alert Wednesday urging American citizens not to travel to Russia and those living or visiting there to leave immediately.

The advisory comes a week after Russian President Vladimir Putin ordered a partial military mobilization to call up as many as 300,000 reservists amid a string of setbacks in Russia’s war against Ukraine.

Wednesday’s alert is not the first time the State Department has cautioned against U.S. citizens being in Russia since the war began in February, but the latest warning says, “Russia may refuse to acknowledge dual nationals’ U.S. citizenship, deny their access to U.S. consular assistance, prevent their departure from Russia, and conscript dual nationals for military service.

“U.S. citizens should not travel to Russia and those residing or travelling in Russia should depart Russia immediately while limited commercial travel options remain,” the security alert added.

Putin’s order has sparked an exodus of Russian nationals fleeing the country to avoid being sent to war. More than 194,000 people have fled to neighboring Georgia, Kazakhstan and Finland — most often by car, bicycle or on foot — in the past week. 

According to the online service Yandex Maps, the traffic jam leading to Verkhny Lars, a border crossing into Georgia from Russia’s North Ossetia region, stretched more than 9 miles Tuesday. Similarly long queues were reported at some crossings into Kazakhstan.

Finland has since moved to bar Russian tourists from entering the country. Estonia, Latvia and Lithuania closed their borders to most Russians before Putin’s announcement, citing domestic support for the war within Russia.

The U.S. Embassy said commercial flights out of Russia are “extremely limited” and “often unavailable on short notice.” The embassy said highways are still open and that U.S. citizens should make independent travel arrangements as soon as possible, adding it “has severe limitations on its ability to assist U.S. citizens, and conditions, including transportation options, may suddenly become even more limited.”

The State Department also is warning against U.S. citizens participating in anti-war protests in Russia. Some Americans have been arrested during demonstrations, it said.

“We remind U.S. citizens that the right to peaceful assembly and freedom of expression are not guaranteed in Russia,” the security alert said. “Avoid all political or social protests and do not photograph security personnel at these events.”

The Associated Press contributed to this report.