The U.S. Embassy in the Balkan state of Montenegro was attacked Thursday by an individual armed with a hand grenade, who hurled the explosive at the compound before blowing himself up.

The area was sealed off by the police and the embassy warned Americans to avoid the area because of “an active security situation.”

“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.

The government of Montenegro said an unknown assailant threw the grenade into the embassy compound in the evening and then blew himself up with another explosive device.

There are no reported deaths except of the attacker.

The New York Times reported that a witness saw the man throw the object over the wall at around midnight. The embassy was closed at the time of the attack.

Security officials swept the grounds and found no other threats. Employees were told to stay home on Thursday, the paper reported.

The European Union 2016 report claimed that roughly 20 Montenegro nationals went on to fight in Syria and Iraq since 2012. It remains unclear how many of them returned to the country.

The report urged the government of Montenegro to improve government agencies to “monitor possible terrorist threats, including radicalized Montenegrin nationals returning from battlefields.”

Last month, a court sentenced one Montenegro national for fighting for the Islamic State. He was given a six-month jail term.

Several other people, including two Russian secret service operatives, meanwhile, are on trial on charges that they wanted to overthrow the government in 2016 over its pro-Western policies.

Montenegro borders the Adriatic Sea in southeastern Europe and its capital is Podgorica. It joined NATO last year.

The U.S. established diplomatic ties with the tiny Balkan state in 2006 after it split from much larger Serbia.

The Associated Press contributed to this report.