Isis has claimed responsibility for a suicide bomb attack on an army camp in Yemen, which has killed at least 54 people, the health ministry said.
A spokesperson for the medical charity Medecins Sans Frontieres said at least 60 other wounded people had been brought into a hospital run by the charity in Aden.
Isis's Amaq news agency said the attack had killed about 60 new recruits.
"Around 60 dead in a martyrdom operation by a fighter from Islamic State targeting a recruitment centre in Aden city," the statement said, without giving further details.
A security source told Reuters the attack targeted a school compound where conscripts of the Popular Committees, forces allied to the internationally recognised President Abd-Rabbu Mansour Hadi, were gathered for breakfast.
Witnesses said the suicide bomber entered the compound behind a truck that had brought breakfast for the conscripts, who had queued for the meal.
"Bodies and body parts are scattered all over the place," said Mohammed Osman, a neighbour who rushed to the scene. "It was a massacre," he added.
Ahmed al-Fatih, who had been working at the centre, said security at the site was lax.
"There was no consideration of security," he said. "So it was easy for al-Qaida or Daesh to pull off such an act," he added, using an Arabic acronym to refer to Isis
Islamist militants have exploited an 18-month-old civil war between the Houthis and Hadi's supporters and launched a series of attacks targeting senior officials, religious figures, security forces and compounds of the Saudi-led Arab military coalition, which supports President Hadi.
Last month, the governor of the southern Yemeni city of Aden survived a car bomb attack targeting his convoy, the latest attempt on the city's top official.
In May, a suicide bomber killed at least 40 army recruits and injured 60 others when he rammed a booby-trapped car at recruits lined up to enlist for military service at a compound in Aden.
Yemen's civil war has pitted the internationally recognised government and a Saudi-led coalition against rebels and army units loyal to a former president.
The UN and rights groups estimate at least 9,000 people have been killed since fighting escalated in March 2015 with the start of Saudi-led airstrikes targeting the Houthis and their allies. Some three million people have been displaced inside the country, which is the poorest in the Arab world.
Additional reporting by agencies
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