VILNIUS, Lithuania — The Biden administration is urging U.S. citizens in Belarus to depart the country immediately and warned against travel there in a statement published Monday.

The updated travel warning comes after bordering countries Lithuania, Latvia and Poland have stepped up security along the border over concerns about Russian Wagner mercenary forces exiled in the country.

The State Department, in its warning, encouraged Americans still in Belarus to depart the country immediately and categorized the country as a Level 4 risk, the highest security warning.

Belarus’s longtime leader Alexander Lukashenko, known as Europe’s last dictator, has been a key facilitator of Russian President Vladimir Putin’s war in Ukraine, and is under a catalog of U.S. sanctions for human rights abuses and political repression against Belarusian people who challenged his claim to election victory in 2020.

The U.S. mission in Belarus is scaled down and only handles emergency American Citizen Services.

Lukashenko’s welcoming of Wagner forces in a deal with Putin that ended the mercenary group’s short-lived rebellion against the Kremlin has raised concern in NATO-member countries on its border.

“Do not travel to Belarus due to Belarusian authorities’ continued facilitation of Russia’s unprovoked attack on Ukraine, the buildup of Russian military forces in Belarus, the arbitrary enforcement of local laws, the potential of civil unrest, the risk of detention, and the Embassy’s limited ability to assist U.S. citizens residing in or traveling to Belarus,” the State Department wrote in its warning.

Last week, Lithuania closed two of its six border crossings with Belarus. The State Department urged Americans to travel through the remaining, open border crossings, warning that the Polish, Lithuanian, and Latvian governments have stated that further closures of border crossings with Belarus are possible.

Poland has one remaining border crossing with Belarus open, while Latvia has two crossings open.

Both Poland and Latvia have increased troops at their borders with Belarus. They also accuse Lukashenko of weaponizing migrants from Middle Eastern countries by flying them to Belarus and sending them across the border.