The attack follows signs that peace talks initiated by the country's new federal government with leaders of the Pakistani Taliban have hit a snag.
 
The fighters are demanding that the Pakistan army withdraw from their strongholds along the Afghan border.
 
Pakistan saw a wave of suicide bomb attacks after an army assault on the Lal (Red) Mosque in the capital Islamabad last July.
 
However, there had been a lull since the formation of the new government in March.
 
The government, led by the party of Benazir Bhutto, the assassinated former prime minister, has begun talks with elders of ethnic Pashtun tribes along the Afghan border.
 
A leader of the Pakistani Taliban announced a ceasefire last month but later said they were rejecting negotiations mediated by the elders after the government refused to withdraw troops from their stronghold areas.