Peshawar (Agencies): A teenage suicide bomber in school uniform penetrated a Pakistani army training centre at Mardan in northwest region on Thursday killing 27 soldiers and leaving 40 others wounded.

"It was a suicide attack by a 12-year-old bomber in school uniform," top police officer Abdullah Khan said on the early morning attack on the army's elite Punjab Regimental Centre at Mardan, 60 kms northeast of Peshawar.

Thirty-one army personnel were killed and 40 others injured, most of them critically in the powerful blast at 0815 am, which could be heard several kms away. An army spokesman confirmed the incident.

Police said the condition of some of the injured was critical and the toll could go up. The responsibility for the hit was claimed by Tehreek-e-Taliban, who threatened to carry out even "bigger strike" to avenge US drone strike and military operation in the region.

The hit on the Punjab Regimental Centre was one of the worst strikes on the Pakistan army deeply involved for last two years in operations in the restive Khyber-Pakhtunkhawa province bordering Afghanistan to flush out Taliban militants.

Khan said the schoolboy managed to sneak into the sprawling heavily-guarded compound carrying a lethal payload apparently in his school bag and triggered the explosion as the troops were readying for the daily parade.

Television quoted witnesses as saying that the blast was so powerful that it blew soldiers away from the ground. The bomber was able to sneak into the centre as he was wearing uniform of school located bang opposite the army facility.

Superintendent of Police Sirajul Hasan said that the boy was carrying 9 kg of explosives and the legs and body parts of the teenage bomber had been found.

But there was conflicting reports about the identity of the bombers. While police and military officials said the strike was carried out by a schoolboy, the Taliban claimed that it was the handiwork of a soldier, who had turned over.

It was not immediately clear how the bomber got into the heavily guarded centre undetected. An attack on the same facility in 2006 had killed 35 soldiers.

Troops sealed off the area and even policemen had a difficult time getting through. The local army hospital declared an emergency as ambulances rushed in casualties.

Some of the critically injured army personnel were flown to military hospitals in Peshawar and Rawalpindi.
 
The forces have taken charge of rescue operations and civilian rescue agencies and media were not allowed entry into the heavily protected military facility.

Mardan is 50 kilometres away from the Mohmand tribal district where the army recently launched a major attack.

Officials have said more than 25,000 people have fled the area in the past one week.

President Asif Ali Zardari and Prime Minister Yousuf Raza Gilani condemned the attack. They said "such cowardly attacks cannot affect the morale of the security agencies and the resolve of the nation to eradicate terrorism."