The famously remote city on the edge of the Sahara is now controlled by Ansar Dine, an Islamist group with links to a regional al-Qaeda affiliate - Al-Qaeda in the Islamic Maghreb (AQIM).

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Yet there is speculation that it could be retaliation for France's recent intervention in Mali, where Islamist groups and members of al-Qaeda's North Africa branch - al-Qaeda in the Islamic Maghreb (AQIM) - had taken control of the country's vast northern desert region.

BBC: Is France under attack in Africa?

Abou Zeid - whose death is still to be confirmed by DNA evidence - is said to be second-in-command of al-Qaeda in the Islamic Maghreb (AQIM), which is fighting foreign forces in Mali.

BBC: Islamist militant Mokhtar Belmokhtar 'killed in Mali'