Police in southern Pakistan say a powerful bomb ripped through an Islamic school Monday, killing six students and wounding at least four others.

Authorities said the bomb exploded in a madrassa in southwestern Qilla Saifullah, a town near the Afghan border in the province of Baluchistan.

Investigators said the bomb was concealed in the belongings of an Afghan student who stayed in the school overnight. Officials said it exploded after the person had left.

There was no immediate claim of responsibility for the blast.

Some Pakistani madrassas are seen as breeding grounds for militants fighting foreign forces in Afghanistan and opposed to Pakistani support for U.S. efforts against terrorism.

Police said it was unclear if the explosion was linked to either conflict.

Some information for this report was provided by AFP, AP and Reuters.