British defence sources said the rules of engagement stipulated the NATO troops could only use force in self-defence or if the safety of the soldiers was threatened.

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The president of Chad said Chadian troops killed the commander, while French military sources said earlier that Abou Zeid, a deputy leader of AQIM, was killed in an airstrike in Mali late last month.

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Quoting diplomatic and military sources, BBC West Africa correspondent Thomas Fessy said French troops would take part in the second phase of the Mali operation, namely driving Islamists out of the main towns they occupied.

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Sources said the Taliban may have been watching the troops make preparations to depart and launched their attack at a time of vulnerability.

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