At least two other children were injured in the explosion, The Nation reported.
Officials said terrorists are attacking civilian targets because it is more difficult to hit high-value targets such as government buildings and military bases.
Police officer Ejaz Khan told the Associated Press of Pakistan the bomb was detonated by remote control. He said no one had claimed responsibility for the attack.
Officials said two people were detained following the blast because they couldn't explain what they were doing in the area.
Senior Provincial Minister Bashir Bilour said militants are striking civilian targets out of frustration that they can't attack sites with adequate security.