At least 11 Pakistani soldiers have been killed in a suicide attack in the country's northwestern district of Swat, the army has said.

The bomber targeted the sports area of a military base camp in Kabal town leaving up to 13 soldiers injured, the Inter-Services Public Relations (ISPR) said in a statement on Saturday.

The area has been cordoned off and security forces are searching for possible accomplices of the bomber, the English language newspaper the Dawn reported.

The Pakistan Taliban, known by the acronym TTP, group has claimed responsibility for the attack - the first major attack in over three years.

Swat Valley was under de facto control of TTP until 2009, when an army operation drove them out. During the two years of their control of the area, the TTP had instituted a stricter brand of Islam, carrying out public floggings and executions.

More than 6,000 security forces are deployed in Swat as security has remained a concern since the TTP was pushed out of the area nearly nine years ago, according to the Dawn newspaper.