Two motorcycle gunmen shot dead Col. Saleh Amtheib on Thursday as he relaxed outside his home after lunch. He was the second security officer gunned down in the southern Abyan province in less than a month.
Two of those arrested over the attack were previously suspected of belonging to Al-Qaeda, while the others had been unknown to authorities, the sources said. Security forces also confiscated a gun they said was used in the shooting.
Authorities had initially been uncertain whom to blame for the killing, the sources said. The officer had participated in the government's battles against Al-Qaeda and also in a separate conflict with armed south Yemen separatists.
Yemen, neighbor to top oil exporter Saudi Arabia, has been a growing security concern for the West since a Yemen-based regional arm of Al-Qaeda claimed responsibility for an unsuccessful attempt to bomb a US-bound plane in December.
Yemen has stepped up security measures after accusing Al-Qaeda of a June 19 attack on the police intelligence building in the southern city of Aden, killing 11 people.
