One of the leaders of an Islamist rebel group fighting against France-led troops in Mali has been arrested near the Algerian border by a rival group.

Mohamed Moussa Ag Mouhamed, Ansar Dine's third in command, has reportedly been captured either by the Islamic Movement of Azawad (MIA) militant group, or by the Azawad National Liberation Movement (MNLA) secular separatist Tuareg rebel movement.

Mouhamed is believed to be "the brain of the organisation" and the man responsible for the horrors and violence that have marked Ansar Dine's 10-month-rule over vast swathes of Northern Mali.

"Mohamed Moussa Ag Mouhamed... the one who sowed terror, who ordered people's hands cut off, who supported the strict application of sharia, was arrested by an armed group," a Malian security source told AFP.

"He was the ideologist of Ansar Dine in Timbuktu, the brain of the organisation there. He has been captured in Hallil, near the Algerian border. He is being taken to Kidal," regional official Abdoulaye Toure added.

News of Mouhamed's capture comes just a week after MNLA fighters recaptured the crucial city of Kidal, driving Islamist militants out and up into mountain refuges.

French and Malian forces have now seized the city airport but, to secure the town, Malian Interim President Dioncounda Traore has offered to hold talks with the MNLA. Mouhamed's name is likely to feature in the negotiations.

Authorities believe that Islamists linked to Mouhamed are still holding a number of French civilians hostage somewhere in the mountains around Kidal. The hostages were abducted from uranium mines in neighbouring Niger a few years ago.

MNLA rebels want an independent state in northern Mali called Azawad and played a pivotal role in starting the rebellion against the Malian government last spring.

The MNLA took advantage of a military coup that deposed President Amadou Toumani Toure to seize part of the country. However their successful rebellion was quickly hijacked by Ansar Dine's Islamist rebels who took control of the whole northern Mali, striking an alliance with al-Qaida in the Islamic Maghreb (AQIM) and the Movement for Unity and Jihad in West Africa (MUJAO).