The bomb, a timed device planted in an auto-rickshaw, went off in a busy area located a short distance from the town hall and a hospital. A car that was passing the area bore the brunt of the blast, which also damaged several nearby shops.

Reports suggested that local legislator Khalifa Abdul Qayyum could have been the target of the attack as he had passed through the city centre shortly before the blast occurred.

Officials in a local hospital said they had received six bodies.

Police said over 20 people were injured in the powerful blast, which was heard several kilometres away. Doctors said six of the injured were in a critical condition.

No group claimed responsibility for the attack. Taliban militants operating in the area are usually blamed for such attacks in Dera Ismail Khan.

President Asif Ali Zardari and Prime Minister Yousuf Raza Gilani condemned the attack and directed authorities to apprehend those responsible for the blast.

Dera Ismail Khan, a major city in the North West Frontier Province, has witnessed suicide attacks on security forces in recent months. The city has also been rocked by sectarian tensions.