A female French-Swiss aid worker was kidnapped in the city of Gao in northern Mali on Saturday afternoon, a spokesman for the Ministry of Security said.

It was not clear who was responsible for the act, or why the aid worker was taken, said Commandant Baba Cissé. The desert nation has been beset by attacks from resurgent Islamist groups like al Qaeda in the Islamic Maghreb (AQIM) this year, especially in the north.

A French diplomatic source told Reuters that Paris was aware of reports of a kidnapping on Saturday and was trying to verify the information.

A local radio station in Gao said the aid worker was affiliated with Aide Gao, a small nonprofit that helps children suffering from malnutrition. She was taken by a group of men who drove off in a Toyota pickup truck, the radio station said.

Aide Gao was not available for comment on Saturday evening.

Gao - seized by Islamist militants in 2012 before French forces drove them out a year later - is considered the best secured town in northern Mali with multiple U.N., French and Malian army checkpoints along main roads.

Even so, the city comes under fire. Last month, the offices of the U.N. peacekeeping mission located next to the Gao airport terminal were razed by a truck-bomb explosion which forced the airport to close.

Mali's government signed a peace deal last year with secular armed groups, but Islamist militants pledging allegiance to both al-Qaeda and Islamic State have fought on and launched dozens of attacks on Western targets in recent months.

Even the peace deal with secular fighters has been broken many times, adding to difficulties faced by U.N. forces in stabilizing the former French colony in West Africa.