An official says militants have attacked a United Nations base in northern Mali, killing at least three people and injuring 30 others.

Olivier Salgado, spokesman for the U.N. mission in Mali, said shelling hit the camp in Kidal early Friday.

Resident Ibrahim Ag Mohamed said that after the explosions U.N. helicopters were seen in the sky and he could hear the exchange of fire outside the city.

No group has claimed responsibility for the attack, but it bares the marks of Islamic extremist Al Qaeda in the Islamic Maghreb.

The group claimed responsibility for an attack at a U.N. mission police base on Feb. 5 in Timbuktu that killed a Malian soldier.

The Kidal U.N. base was last targeted by mortars on Nov. 28, killing three people.