The United States has urged its citizens to immediately leave Belarus, citing a buildup of Russian troops along the border with neighboring Ukraine.

The travel advisory, issued Monday, came the same day that Washington announced it was closing its Kyiv embassy and relocating staff to the Ukrainian city of Lviv 335 miles (540 kilometers) away due to a “dramatic acceleration” in the buildup of Russian forces.

Last week, Washington warned that Russia could attack “any day now.”

“Due to an increase in unusual and concerning Russian military activity near the border with Ukraine, U.S. citizens located in or considering travel to Belarus should be aware that the situation is unpredictable and there is heightened tension in the region,” the advisory said.

It also noted that last month, the State Department ordered all family members of the Minsk embassy to leave.

American citizens have already been urged to leave Ukraine, with the West accusing Russia of sending more than 100,000 soldiers to encircle the former Soviet state.

In addition to fears of a possible military conflict on the border, Washington’s “do not travel” advisory for Belarus flagged the risk of detention, arbitrary enforcement of laws and Covid-19 entry restrictions as reasons for Americans to get out.

“The U.S. government’s ability to provide routine or emergency services to U.S. citizens in Belarus is already severely limited due to Belarusian government limitations on U.S. Embassy staffing,” it said