The attack was claimed by the Tehreek-i-Taliban Pakistan (TTP) in an email to journalists, AFP reported.

ISPR had earlier said three soldiers were martyred in the attack. The death toll rose after seven critically injured soldiers succumbed to their injuries. An officer is among those martyred in the attack, ISPR said.

Initial reports suggested that the bomber blew himself up in a ground where soldiers were playing volleyball.

According to some sources, as many as 16 people were injured in the blast. All the injured were shifted to Combined Military Hospital Saidu Sharif.

Security forces have cordoned off the area and are searching for possible accomplices of the bomber.

The picturesque Swat Valley was under the de facto control of TTP in 2007-2009. They imposed their harsh brand of sharia law, and carried out public floggings and executions until a military operation drove them out.

The area has seen sporadic militant attacks since, including assassinations of local leaders who cooperate with the government. Today's bombing is the first major attack in over three years in the valley.

Although peace had returned to Swat after the 2009 army operation, security has been a primary concern in the region. Police and armed forces personnel jointly man several checkpoints. There are approximately 6,000 policemen in Swat and most of them are deployed on checkpoints.

A few days ago, Swat police claimed to have arrested two militants, in the same area, allegedly involved in anti-state activities during spillover of militancy to the Swat valley.

According to Kabal police, following a tipoff, they along with the CTD police raided a house in Kabal where they found a wanted militant, Siraj Khan, and arrested him. In the meantime, the CTD police carried out another raid at Shawar area in Matta tehsil and arrested a militant commander, Mohammad Ali Shah, who was allegedly involved in attacks on security forces.