A suicide bomber disguised as a policeman blew himself up inside a police training camp in Somalia’s capital Mogadishu on Thursday and killed at least 15 officers, officials said.

 Police spokesman Major Mohamed Hussein said the attacker had explosives strapped to his body and infiltrated the General Kahiye Police Training Academy during an early morning parade.

“So far 15 have died and 17 others were injured,” Abdullahi Nur, another police official, told Reuters.

Earlier, the head of a local ambulance service said they had moved the bodies of 13 victims as well as 15 injured people.

The militant Islamist group al Shabaab claimed responsibility for the attack and gave a higher death toll.

“We killed 27 police (officers) and injured more,” Abdiasis Abu Musab, the group’s military operations spokesman, told Reporters. Al Shabaab carries out frequent bombings in Mogadishu and other towns.

The group, which is allied to al Qaeda, is waging an insurgency against the U.N.-backed government and its African Union allies in a bid to topple the weak administration and impose its own strict interpretation of Islam.