Unknown attackers fired rockets at a United Nations peacekeeping base in northern Mali on Saturday, killing three people inside, the U.N. said, in the latest sign that the West African country’s Islamist insurgency is intensifying.

French troops and the 10,000-strong U.N. force, known as MINUSMA, are struggling to stabilize the former French colony. Islamist militants attacked a hotel in the capital Bamako on Nov. 20 and killed 20 people, in their bloodiest attack yet in the country’s south.

Desert-based jihadists regularly launch rockets and missiles at northern U.N. bases, especially around full moon when the lighter nights make it easier to target the camps, although it is rare for the missiles to land inside the walls.

“They fired rockets from around 4 a.m. inside the MINUSMA camp,” Olivier Salgado, Deputy Chief of Communication in the peacekeeping mission, told Reuters.

“We have three dead and four seriously injured,” he said, adding that there were a total of 20 wounded and that medical evacuations were under way from the base in the town of Kidal.

The United Nations later identified the victims as two Guinean peacekeepers and a contractor from Burkina Faso.

“The members of the Security Council called on the Government of Mali to swiftly investigate this attack and bring the perpetrators to justice, and stressed that those responsible for the attack should be held accountable,” it said, adding that the attacks may constitute war crimes.

French news agency AFP said that Malian Islamist rebel group Ansar Dine had claimed responsibility for the attack.

Ansar Dine is not one of the three Islamist militant groups – al Qaeda in the Islamic Maghreb, its splinter group al Mourabitoun and Massina Liberation Front (MLF) – that claimed last week’s attack on the Radisson Blu hotel in Bamako, where the victims included Russians, Chinese and an American. Security analysts say the groups could be collaborating.

Bursts of gunfire rang out shortly after the rockets landed, as well as mortar fire coming from inside the camp, according to a witness in Kidal.

A security source in north Mali who wished to remain anonymous said the Kidal camp had received a warning two days before the attack from an unnamed jihadist group. A local deputy for Kidal, Ahmoudene Ag Ikmasse, also blamed radical Islamists.

Northern Mali was taken over by Islamist fighters, some with links to al Qaeda, for most of 2012. They were driven out by a French-led military operation a year later, but violence has continued and spread into formerly safe areas in the south.

Some analysts say the spike in jihadist attacks is designed to disrupt the implementation of a peace deal signed between various northern armed groups and Mali’s government in June.

“I want to reiterate that these attacks will not impede the determination of the United Nations to support the Malian people and the peace process,” said Mongi Hamdi, U.N. Special Envoy for the Mali mission.

A French soldier, part of the 3,500-strong Barkhane anti-terrorism force operating across the Sahel, and a U.N. peacekeeper were killed by landmines this week.

Germany has said it is willing to send up to 650 soldiers to bolster the U.N. force, which has yet to reach its full strength of 12,680 men and is mostly made of African troops.