Some 38 Yemeni troops were killed Monday in a series of attacks in the south-eastern city of Mukalla, a local security official said on condition of anonymity.
The attacks were claimed by the Islamic State extremist group, whose Aamaq news agency said they were carried out by "commandos of the Islamic State."
The security official said two suicide attackers and a number of bomb blasts targeted an intelligence base in the city as well as two other areas.
Another 24 people, including civilians, were injured in the attacks, he said.
The official said the dead troops were from the Hadhrami Elite units, a recently formed local force which, backed by Gulf troops, recaptured Mukalla from al-Qaeda jihadists in April.
Both Islamic State and al-Qaeda have expanded operations during Yemen's civil war, which pits mainly Shiite Houthi rebels against a range of opponents, including the internationally recognized government of President Abd Rabu Mansour Hadi.
Islamic State also claimed responsibility for suicide bombings in May that killed 73 would-be army recruits in Mukalla and the southern port city of Aden, Hadi's temporary capital.
The Yemeni government and the rebels started peace talks in Kuwait in April, but little progress has been made.