Gunmen in Mali have killed a senior military officer who was investigating an al-Qaida-affiliated group.

Security officials said Lieutenant Colonel Lamana Ould Bou was gunned down in his home in the central city of Timbuktu Wednesday night.  

His relative told the French news agency (AFP) that armed men parked a car in front of Ould Bou's house and two of them went inside.  He said the gunmen fired three bullets at the officer before fleeing the scene.

Ould Bou had a key role in Mali's recent arrest of several members of the group al-Qaida of the Islamic Maghreb.  

The group said it killed a British hostage, Edwin Dyer, on May 31.

Militants kidnapped Dyer and five other people near the border of Mali and Niger about six months ago.  

The group had demanded that Britain release Jordanian cleric Abu Qatada in exchange for Dyer.

The group has released four other hostages, but is still holding a Swiss tourist.

After Dyer's murder, Mali's government announced what it called a pitiless struggle against al-Qaida of the Islamic Maghreb.

Some information for this report was provided by AFP and AP.