A suicide bomber killed at least 14 soldiers in Aden on Wednesday, in the latest attack on Yemen's second city claimed by jihadists of the Islamic State group.
The southern port city has been the headquarters of forces loyal to President Abedrabbo Mansour Hadi and his backers in a Saudi-led military coalition but has seen growing violence by IS and its jihadist rival Al-Qaeda.
"A man detonated his explosive vest among soldiers," a military source said.
The troops were attending a training session run by Sudanese forces of the Saudi-led coalition, another military source said.
The bomber, who was disguised as a soldier, attacked the Ras Abbas camp in the west of Aden.
After the attack, panicking soldiers grabbed their weapons and fled the camp, witnesses said.
The little-known "Aden and Abyan Province" branch of IS said the suicide bombing was carried out by one of its militants and alleged it killed 20 "apostate" soldiers.
It came a day after Al-Qaeda claimed an attack on the convoy of Aden's governor and police chief in which four jihadists were killed.
Since March last year, when the Saudi-led coalition intervened in support of Hadi, IS has ramped up its operations in Yemen.
Its rival Al-Qaeda also has a significant presence in the south and southeast.
In October, IS claimed its first attacks in Aden -- a series of bombings that targeted the government's temporary headquarters and two military camps run by the coalition in which 15 people were killed.
Coalition forces have been training pro-government militiamen whom Hadi merged into the army after they drove Iran-backed rebels out of Aden and other southern provinces last year.
The United Nations says more than 6,100 people have been killed and 29,000 wounded since the coalition began its intervention, about half of them civilians.