"Twenty soldiers were killed in the armed attack on an army checkpoint" near Reida, 135 kilometres east of the provincial capital Mukalla in the south, Saba said.
Security sources earlier put the toll at eight dead and six wounded, with one source saying the assault bore all the hallmarks of Al-Qaeda in the Arabian Peninsula (AQAP).
One source said the assault was carried out by gunmen aboard several vehicles.
"The attackers would appear to be in Al-Qaeda," the second military source said of AQAP, which the United States views as the jihadist network's most dangerous franchise.
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On March 18, a suspected Al-Qaeda suicide car bombing at a military intelligence headquarters killed one person and wounded 13.
The attacker detonated the car outside the gate to the security building in Tuban, 15 kilometres north of Aden, killing a guard.
That attack came two days after three suspected Al-Qaeda militants, one a Saudi, were killed in the southern province of Shabwa when a car bomb they were preparing apparently detonated accidentally.