An unknown person threw an explosive device at the United States embassy in Montenegro today before blowing himself up, the European nation's government says.
Messaging in English on its official Twitter account, the government said half an hour after midnight (10:00am AEDT) the individual "committed suicide with an explosive device".
"Immediately before, that person threw an explosive device from the intersection near the Sport Centre into the US embassy compound," it added.
"Most probably, the device was a hand grenade," adding that a police investigation was underway.
Witnesses in capital city Podgorica said a police vehicle blocked the street where the embassy was located, adding that no damage was visible.
The embassy warned US citizens to stay away from the embassy until further notice due to an "active security situation".
"The US embassy in Podgorica advises US citizens there is an active security situation at the US embassy in Podgorica," it said on its website.
"Avoid the embassy until further notice."
Earlier, media in Montenegro had said the attack occurred minutes before midnight.
Montenegro, the smallest of all former Yugoslav republics, was the 29th country to join NATO last May