Al-Qaeda in the Islamic Maghreb (AQIM) executed Thursday a guide for the Malian customs service whom they kidnapped this week with a Mali soldier, a security official and a relative told AFP.

The man, who acted as a guide through the vast northern Mali desert, was executed after militants found he was carrying documents from a Western embassy based in the capital, Bamako, they said.

Known as Merzuk, he was kidnapped with a Malian soldier in the Kidal region of northern Mali on Tuesday.

The nature of the documents he was said to be carrying and the embassy concerned were not clear.

The kidnappers had a "score to settle with him", said the relative and security official in the Kidal governor's office who announced the execution.

Moctar Ag Klinine, a relative of one of the captured men, said Wednesday Al-Qaeda had accused the pair of "being hostile".

An official from the security ministry confirmed the abduction, saying: "There were others with the customs guide and the member of the national guard who were spared. This means they were targeted."

Another security source said one of those abducted had been injured during the seizure.

AQIM carries out attacks and kidnappings in a vast area of the Sahel desert bordering Mauritania, Algeria, Mali and Niger.

The North African branch of Al-Qaeda in July claimed responsibility for the execution of a French hostage, Michael Germaneau, 78, who was kidnapped in Niger in April before being transferred to Mali.

AQIM said the murder was revenge for a failed Franco-Mauritanian raid to try and find Germaneau, in which seven jihadists were killed.

AQIM is also still holding two Spanish hostages in northern Mali. Albert Vilalta and Roque Pascual were abducted in Mauritania in November 2009.