The U.S. Embassy in Podgorica, Montenegro has informed U.S. citizens of an “active security situation” after an attacker lobbed an explosive at the compound.

“The U.S. Embassy in Podgorica advises U.S. citizens there is an active security situation at the U.S. Embassy in Podgorica. Avoid the Embassy until further notice,” said an alert sent from the embassy on Thursday, local time.