The clash erupted when "Al-Qaeda gunmen" attacked the military headquarters in the city of Sayun, a stronghold of jihadists, the military official said.
The army had reinforced its positions in Sayun ahead of an anticipated operation against militants in the city.
Two soldiers were yesterday killed and two wounded when gunmen attacked forces heading towards Sayun, a military official said. The defence ministry said 18 militants were killed in the confrontation.
On Monday, four soldiers died in a ambushes in Hadramawt, while four policemen were killed on Saturday in an attack on a checkpoint in Shabwa.
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Security services blame the attacks on Al-Qaeda in the Arabian Peninsula, which has been branded by Washington as the extremist network's deadliest franchise.
In late April, the army launched a ground offensive against AQAP in Shabwa and nearby Abyan provinces.