An assailant with knives attacked a guard outside the Israeli Embassy in Belgrade and was killed just after midnight on Wednesday, Serbian police said.

Axar.az reports, citing The Associated Press, that Interior Minister Ivica Dacic said that police were treating the incident as a “terrorist attack” and had raised the terror threat to the highest level and stepped up police presence at key locations.

He said the attacker was a minor and had two knives. He attacked the member of the Gendarmerie, shouting Allahu Akbar, or “God is great” in Arabic. Dacic added that the police officer, who was slightly wounded to the face, killed the assailant in self-defense.

The attacker was believed to be from the western Serbian town of Sabac, Dacic said.

He said that Serbia’s security agencies had been monitoring the attacker, who he said was a supporter of the Islamic State group. Dacic said that “he kept the black flag in support of the Islamic State on his Instagram” account.