Suspected Al Qaeda militants shot dead a Yemeni intelligence officer in the southern city of Mukalla on Monday, a security official told Reuters.
Al Qaeda in the Arabian Peninsula (AQAP) has carried out a series of hit-and-run attacks since the Yemeni army drove it from its southern strongholds in Abyan and Shabwa provinces in April.
Gunmen on a motorbike killed Colonel Ahmed Radman, a member of Yemen's political security division, the source said. At least 25 other senior officers have been killed in Yemen this year.
Another colonel was shot dead in the capital Sanaa on Saturday and an officer and a local official were killed in two Southern provinces on Sunday, officials told Reuters.
The West is concerned AQAP could use Yemen, which borders major oil producer Saudi Arabia, as a base for international attacks.
Apart from the fight against al Qaeda, the government faces a push by southern separatists for independence and battles with rebels from the Shi'ite Muslim Houthi movement, which is trying to extend its control over the north.
Yemen's military has struggled to face the challenge after splitting apart in the wake of anti-government protests which forced veteran president Ali Abdullah Saleh to step down in 2011.