A powerful early morning suicide truck bomb devastated a hospital in southern Afghanistan on Thursday, killing at least 20 people and wounding more than 90 others, an official said.

The Taliban took responsibility for the attack, which destroyed part of the hospital in Qalat, the capital of southern Zabul province, and left a fleet of ambulances broken and battered.

Residents, many of whom had come to see their sick family members, used shawls and blankets to carry the wounded inside the destroyed building, while authorities scrambled to take the worst of the wounded to hospitals in nearby Kandahar.

In the early hours after the explosion there were contradictory figures of the dead and wounded. The provincial governor's spokesman Gul Islam Seyal put the death toll at 12 but said authorities were on the scene sifting through the debris. Atta Jan Haqbayan, head of the provincial council, put the death toll at 20.

The Taliban, who have been carrying out nearly daily attacks since peace talks with the United States collapsed earlier this month, said the target was a nearby government intelligence department building.

Haqbayan said the wall of the National Security Department (NDS) building was damaged. He couldn't say whether any personnel were among the casualties.