Yemeni officials and tribal leaders say al-Qaida militants targeted a military camp in southern Abyan province, killing at least 20 troops.
The militants attacked the camp with rocket propelled grenades and automatic rifles around midnight, setting off clashes that lasted until early morning on Friday.
The troops targeted are members of a force trained by the United Arab Emirates, a member of the Saudi-led coalition fighting the Houthi rebels since 2015.
The officials spoke on condition of anonymity as they were not allowed to talk to reporters.
The tribal leaders asked to remain anonymous for fear of retaliation.
Al-Qaida's Yemen branch has exploited the chaos of Yemen's civil war.
The attack came a day after Yemen's southern city of Aden was hit by double attacks that killed 51 people.