According to Khalid Khan, a local administration official, hundreds of elders from five tribes had gathered at a jirga - a traditional tribal council - to discuss "efforts to check growing Taliban activity in the area".
   
Khan also said the elders and local officials had finished their talks when the bomb exploded.
  
He said: "There were heavy casualties - we are shifting them to  Peshawar."

Violent region

The town of Darra Adam Khel had recently become a stronghold of Lashkar-e-Jhangvi, a pro-Taliban movement said to have links to al-Qaeda.

In January, Pakistani forces mounted a major offensive to defeat fighters who had occupied a major road tunnel in the area.

At least 13 soldiers and 50 fighters were killed in the heavy fighting.