The U.S. on Monday issued a top-level advisory telling American citizens to leave Russia immediately and cease travel to the country as Russia’s war against neighboring Ukraine continues, citing risks of harassment and wrongful detention for Americans specifically. 

“Do not travel to Russia due to the unpredictable consequences of the unprovoked full-scale invasion of Ukraine by Russian military forces, the potential for harassment and the singling out of U.S. citizens for detention by Russian government security officials, the arbitrary enforcement of local law, limited flights into and out of Russia, the Embassy’s limited ability to assist U.S. citizens in Russia, and the possibility of terrorism,” reads the alert. 

“U.S. citizens residing or travelling in Russia should depart immediately. Exercise increased caution due to the risk of wrongful detentions.”

The warning marks the highest level, Level 4, of alerts issued by the State Department, which ranges from exercising precaution to ceasing all travel. 

It comes as the Russia-Ukraine war nears its first anniversary on Feb. 24 and amid concerns that Moscow is amassing troops for an offensive that could coincide with that one-year mark. 

The U.S. urged its citizens to leave the country just days after the invasion and again with a security warning in September, as Moscow ordered a call-up of reservist forces to renew its advances against Ukraine.

Reuters reported Monday that Kremlin spokesman Dmitry Peskov dismissed the U.S. warning, saying it’s “not a new thing.”

The word of caution about wrongful detentions follows the high-profile prisoner swap of Russian arms dealer Viktor Bout for U.S. basketball star Brittney Griner, who had been sentenced to nine years in a Russian penal colony on drug possession charges. Griner’s trial and sentencing were decried by U.S. and elevated the plight of former U.S. Marine Paul Whelan, who is being held by Moscow on suspicion of spying. 

Updated at 9:08 a.m.