At least 11 Pakistan Army officers and soldiers were killed and 13 others injured in a suicide blast inside an army unit in Swat district of Khyber Pakhtunkhwa province on Saturday, defence officials said.

The Inter-Services Public Relations said in a statement that the attack happened in a sports area of the unit in Kabal town of Swat.

The death toll may further increase as several injured were in a critical condition, health officials said.

The attack happened when soldiers were playing volleyball. The injured soldiers have been shifted to Kabal hospital.

Outlawed militant group Tehreek-e-Taliban claimed the attack, according to the media reports.

Prime Minister Shahid Khaqan Abbasi has strongly condemned the suicide attack, the Prime Minister’s office said.

Abbasi said that no cowardly attack can deter Pakistan in pursuing struggle against the menace of terrorism to its logical conclusion. “We will continue our fight till the last trace is rooted out,” he said in a statement.

Pakistani security forces had cleared Swat valley in a major operation in 2009. Earlier the Pakistani Taliban militants had strong influence in most parts of Swat.