Armed men kidnapped a Swiss missionary from her home in Timbuktu on Friday, nearly four years after she was abducted by Islamist militants from the same house, Malian and Swiss authorities said.

There was no immediate claim of responsibility but Al Qaeda in the Islamic Maghreb (AQIM) is active in desert areas north of the city and has a history of seizing foreigners and demanding ransoms.

In April 2012, militants kidnapped Beatrice Stockly and released her days later. She returned to her work as a missionary. A resident of Timbuktu who knows Stockly told Reuters she had again been abducted.

"I confirm that a European woman was kidnapped in Timbuktu at 3.30 a.m. (0330 GMT). A neighbour alerted the security forces around 6 a.m.," said army spokesman Souleymane Maiga.

Four vehicles were used in the kidnap, said a military source in Timbuktu who declined to be identified.

"One vehicle parked in front of the house and armed men got out and abducted the woman, while the other three cars secured the area from a distance," said the source.

French forces drove Islamist fighters from major urban centres in 2013 but they have intensified their insurgency with a series of attacks and roadside bombings last year.

Two militants attacked a luxury hotel in the capital Bamako on Nov. 20, killing 20 people, many of whom were foreigners.

Three Islamist militant groups including AQIM claimed responsibility for the hotel attack, which showed the militants extending their reach beyond the north.

In a separate incident, an unidentified gunman shot three people dead outside a Christian radio station in Timbuktu in December. A veteran jihadist called for a return to Islamic sharia law at a recent meeting attended by hundreds of locals near Timbuktu, an AQIM video showed this week.

Dozens of Westerners were abducted by desert militants in West and North Africa in the five years before the French military operation in Mali in 2013.

There has been a lull since then, with many foreigners too frightened to visit. In the last known abduction attempt, two French journalists from Radio France International were killed in Kidal, northern Mali, in Nov. 2013.

Two Western hostages kidnapped in north Mali in 2011 are still being held by al Qaeda militants.

The Swiss foreign ministry formed a task force when it heard about Friday's kidnapping and was working for the woman's safe release, a statement said, adding that since 2009 it had advised against travel to Mali because of the high risk of kidnapping.

"After the kidnapping of 2012, the ministry had pointed out to the affected Swiss national the high personal risk in Mali ... and strongly discouraged her from another stay in Mali," it said.

France continues to fight militants in Mali and elsewhere in the desert region with a 3,500-strong counter-terrorism force called Barkhane. A 10,000-strong U.N. peacekeeping force is also present in Mali.