Assailants shot dead a senior Yemeni intelligence officer in Marib city east of the capital Sanaa on Friday, a security source said.
Commander Jarallah Salhi was gunned down in the centre of the city controlled by forces loyal to the government in the conflict against Iran-backed Shia Houthi rebels.
The officer had actively taken part in the battle for Marib dam, southeast of the city backed by a Saudi-led coalition.
The Houthis seized Sanaa last year and then advanced south to the second city of Aden, forcing President Abedrabbo Mansour Hadi to flee to Saudi Arabia.
Loyalists of Hadi, who returned to Aden last month, have gained the upper hand in oil-rich Marib province and are now trying to advance on the rebel-held capital.