A suicide bomber killed at least 25 new recruits inside a police compound in the southern Yemeni city of Mukalla on Sunday in an attack claimed by Islamic State, medical and security sources said.
The victims were queuing up to register when the bomb, which wounded 25 others, went off, the sources said.
It was the second deadly blast in four days to hit the city, a hub for al Qaeda before the militant group was pushed out last month in an offensive by Yemeni troops backed by a Saudi-led coalition.
In a message on its online news agency Amaq, Islamic State said Sunday's attacker was a "martrydom-seeker" who had detonated his explosive belt. It said around 40 died in the attack.
The growing Islamist militant threat has led the Houthis and the Yemeni government to embark on peace talks now under way in Kuwait.