PODGORICA: An unidentified man threw an explosive device, probably a hand grenade, at the US embassy building in Podgorica, the capital of Montenegro, around midnight before blowing himself up, the government said on Thursday.

No casualties were reported from the embassy which confirmed a small explosion near its compound. The U.S. State Department said checks were being carried out to ensure all staff were safe.

Policemen with submachine guns and police vehicles were out on the streets near the embassy building on Thursday morning after the incident.

“All appropriate state bodies are undertaking measures and activities with an aim of resolving this case and securing full safety and security of the U.S. embassy’s staff,” Montenegro’s interior minister, Mevludin Nuhodzic, said in a video message, condemning the incident.

Montenegro state television quoting police sources said the attacker was a 43-year old man born in Serbia and residing in Podgorica. Montenegro police declined to confirm media reports to Reuters.

The government, in a tweet, said that about half an hour after midnight “an unknown person” had committed suicide with an explosive device.

“Immediately before, that person threw an explosive device from the intersection near the Sport Center into the U.S. embassy compound.” The device was most probably a hand grenade, it said.

The embassy was closed for issuing visas on Thursday and it warned U.S. citizens to stay away until further notice.

“The U.S. embassy in Podgorica advises U.S. citizens there is an active security situation at the U.S. embassy in Podgorica,” it said on its website.

Montenegro is the smallest of all former Yugoslav republics and became the 29th country to join NATO last May.