A suicide bomber killed 35 Yemeni soldiers and wounded around 50 on Saturday at a military camp in Aden.
The ISIL group claimed responsibility for the attack.
The bomber detonated his explosives belt as hundreds of troops gathered to receive their monthly pay at the barracks in Al Sawlaban near the city’s international airport, a military source said.
Yemeni authorities have for months pressed a campaign against extremists who remain active in the south and east of the country.
ISIL and its militant rival Al Qaeda have taken advantage of a conflict between the government and the Houthi rebels, who control the capital Sanaa, to bolster their presence across much of the south.
The two groups have carried out a spate of attacks in Aden, Yemen’s second city and headquarters of the internationally recognised government whose forces retook the port from the Houthis last year.
Al Qaeda has long been the dominant force in Yemen, but experts say ISIL is seeking to supplant its extremist rival.
In August an ISIL militant rammed his explosives-laden car into an army recruiting centre in Aden, killing 71 people in the deadliest extremist attack on the city in more than a year.
On Monday, Yemeni authorities arrested eight suspected ISIL militants implicated in a spate of attacks targeting security personnel in the city this year.
A Saudi-led coalition, which includes the UAE, has since March 2015 supported loyalist forces and the internationally-recognised government fighting the Houthis and their allies.