DAKAR — Two U.N. peacekeepers and a civilian were killed after unknown assailants fired rockets at a U.N. peacekeeping base in Kidal in northern Mali early on Saturday, a U.N. spokesman said.

"They fired rockets from around 4 a.m. inside the MINUSMA camp," said Olivier Salgado, Deputy Chief of Communication in the peacekeeping mission. "We have three dead and four seriously injured."

French troops and the U.N. force are struggling to stabilize the former French colony where Islamist militants attacked a hotel in the capital on Nov. 20 and killed 20 people.

Three Islamist militant groups — al-Qaeda in the Islamic Maghreb (AQMI), its splinter group al Mourabitoun and Massina Liberation Front (MLF) — claimed the attack on the Radisson Blu hotel. Security analysts say they could be collaborating.

Related: Mali Arrests 2 Suspects Linked to Bamako Hotel Attack

Northern Mali was occupied by Islamist fighters, some with links to al Qaeda, for most of 2012. They were driven out by a French-led military operation, but violence has continued.Other West African governments are also battling Islamist militants. Boko Haram, the leading such group in the region, has this year extended its attacks from Nigeria to neighboring states of Niger, Cameroon and Chad.