The explosion took place in the city of Zinjibar and targeted the convoy of Abdel-Latif el-Sayed, commander of the so-called Security Belt force in the southern province of Abyan
Prime Minister Maeen Abdulmalik Saeed called the explosion a "terrorist attack" and ordered an investigation.
The dead included a high ranking special forces officer and at least 20 others were wounded in the attack.
Earlier this month, at least 89 people were killed in a chemical attack as children foaming at the mouth and adults gasping for last breath.
The attack took place as thousands of evacuees from two besieged government-held towns waited to continue their journey to regime-controlled Aleppo, sources said.