Bomb disposal experts were working to establish whether the blast was a bomb attack or an accident caused by unexploded ordnance.

The blast took place in a garbage dump on the outskirts of Quetta, the provincial capital.

"Two children who worked as garbage collectors were killed. As yet we are not clear about the nature of the blast," Hamid Shakil, a senior police officer, told AFP.

"A bomb disposal squad is examining the site and collecting evidence."

Baqir Shah, a doctor in Quetta's main hospital, said the dead children were between five and eight years old.

Copyright AFP (Agence France-Presse), 2011