MARDAN: A teenage suicide bomber killed up to 31 army recruits at a parade ground on Thursday, an attack the Taliban said was revenge for US drone strikes and local military offensives.

Wearing school uniform, the young teen blew himself up at the parade inside a heavily guarded military compound just outside the town of Mardan, killing the soldiers with shrapnel and explosives, officials said.

The Taliban claimed responsibility and threatened "bigger attacks" in coming days to avenge American drone strikes and Pak military operations targeting militants in the northwestern tribal belt.

"It was a suicide attack. The teenager bomber was on foot and was wearing a school uniform," Abdullah Khan, a senior police officer in Mardan, around 30 kilometres (20 miles) from the regional capital Peshawar, told AFP.

"The death toll has now reached 31 recruits. Thirty-six have been injured, Sixteen of them are critical," Khan told AFP.

"The bomber was 14 or 15 years old. He was not a student at the school inside the regiment. He came from outside but was dressed like the other school boys."

"We proudly claim this suicide attack," Taliban spokesman Azam Tariq told AFP by telephone from an undisclosed location.

"We will continue such attacks on those people who are providing security to the Americans. These attacks are to avenge the drone attacks and military operations in the tribal areas."