At least 20 people have been killed in a suicide bomb attack at the police academy in the Yemeni capital, Sanaa, medics and security officials say.
Police sources said the bomber had blown himself up among a crowd of cadets as they left the academy after classes finished for the day.
Dozens of people were wounded and many ambulances rushed to the scene.
Islamist militants have vowed to launch attacks in retaliation for an ongoing army offensive on their strongholds.
In May, more than 90 soldiers were killed when a suicide bomber dressed in army uniform blew himself up during a parade rehearsal in Sanaa.
Ansar al-Sharia, an offshoot of al-Qaeda in the Arabian Peninsula, said it had carried out the attack - the deadliest in the capital since Abdrabbuh Mansour Hadi was elected president in February.