A suicide attacker blew himself up after throwing an explosive device into the US embassy compound in Podgorica, the Montenegrin government said Thursday.

Authorities in Podgorica have not released any theories as to the motive for the attack in the country which recently joined NATO despite opposition from some of the population and from where a number of jihadists have traveled to Iraq and Syria.

"In front of the US embassy building in Podgorica, Montenegro,an unknown person committed suicide with an explosive device. Immediately before, that person threw an explosive device," the government tweeted, saying the device was "most probably" a hand grenade.

It said the attacker threw the explosive device "into the US embassy compound" from an intersection near a sports center.

A US State Department spokesperson confirmed "a small explosion near the US Embassy compound" saying officials were "working closely with police to identify the assailant(s)."

On its Twitter account, the embassy said it had cancelled all visa services for Thursday, adding that access for US citizens "will be available today on an emergency basis."

A guard at the sports center  said he "heard two explosions, one after another."

"Police came very quickly and the body of a man was taken away," he told AFP.

The heavily-secured embassy building is located on the outskirts of Podgorica's city center, near the secret police headquarters.