Pakistan's interior minister says the siege of a hospital in southwestern Pakistani has ended after security forces stormed the building.

Chaudhry Nisar Ali Khan said forces freed 35 people trapped inside the building, killed four of the attackers and arrested another.

He says four security forces and one top government officials died during Saturday's violence, which began when attackers set off a bomb in a corridor in the hospital's emergency room and then took over areas of the hospital.

The interior minister did not have any information on the identity of the attackers, and there has been no claim of responsibility.