NIAMEY - Suicide bombers struck a barracks and a French-run uranium mine in Niger on Thursday, officials said, killing 20 people and wounding dozens in attacks that showed armed unrest spreading across West Africa.

In Agadez, the largest town in northern Niger, at least 20 soldiers were killed and 16 injured when suicide bombers attacked a barracks at dawn, Defence Minister Mahamadou Karidjo told state radio. Three attackers were also killed. After a fierce gunbattle, security forces returned the town to calm but one attacker was still holding soldiers hostage local officials said.

Further north in Arlit, at least 14 civilians were injured and two Islamists killed in a bomb attack at the Somair uranium mine operated by run by French nuclear group Areva, the minister said. Niger officials said crushing and grinding units had been badly damaged at the Areva plant and uranium production had stopped.

Al Qaeda's north African wing AQIM took five French workers hostage in 2010 at the remote site, 1,200 km (750 miles) north of the capital Niamey.

Karidjo said responsibility for the attack had been claimed by the MUJWA militant group, a West African offshoot of AQIM. The group was part of a loose Islamist coalition which seized control of neighboring north Mali last year before being ousted by a French-led offensive launched in January.

"The situation is under control and the search for the other attackers is under way," Karidjo told state radio. "There will be a 72-hour period of national mourning starting from today."

The suicide attacks were the first in Niger since the offensive in Mali drove Islamist groups there across borders into neighboring Sahel states.

The official ANP state news agency, citing unnamed sources, said the militants had entered Niger via lawless southern Libya, carrying explosive belts which they used in their attack.

Niger's army has deployed some 650 troops as part of a regional West African force in Mali. Islamist suicide bombers have carried out a spate of attacks there in recent months, including one on a Niger barracks this month.