At least 28 people were killed and nearly 160 injured on Friday when a suicide bomber blew himself up in the funeral procession of a Shia cleric in the north-western Pakistani city of Dera Ismail Khan on Friday, sparking angry protests which prompted authorities to impose curfew.

The suicide bomber targeted the funeral procession of cleric Sher Zaman, who was shot dead by unidentified gunmen on Thursday. The attack sparked off street violence with some 1,500 angry protestors demanding that the culprits responsible for the blast and the killing of the cleric be brought to justice.

The district police chief Mohammad Iqbal told media persons that 28 people were killed and 157 injured in the powerful blast. Though the procession had security cover, the bomber emerged from a crowded bus terminal on the route of the procession and blew himself up, he said.

No group claimed responsibility for the blast. Officials said the attack could be linked to sectarian rivalries.

The city has been witnessing a spate of attacks on the minority Shia community and in most of these attacks the bombers have blown themselves up near the religious places or processions.

The protestors on Friday went on a rampage, opening fire and burning a bus and several other vehicles.

Witnesses said the procession was targeted by a suicide bomber aged between 15 and 17 years. The protestors, who claimed authorities had not made adequate security arrangements for the funeral, targeted government offices and security forces. They also damaged a police check post, pelted stones at cars on the roads and snatched cameras from television crews that were covering the incident.

The attack and subsequent protests caused panic and confusion in Dera Ismail Khan and shops and markets closed down soon after the blast. People rushed home and parents to schools to collect their wards.

There were also reports that staff at a hospital, where the injured were taken, fled on seeing the angry protestors.

Friday's attack was similar to another one in Dera Ismail Khan in November last year, when 10 people were killed and over 30 injured when a suicide bomber struck the funeral of a Shia elder.

Earlier this month, one person was killed and 20 others were injured in a blast inside a mosque in Dera Ismail Khan.

The city has witnessed several bomb attacks in the past few months. Six persons were killed and over 20 injured in a bomb attack that targeted a provincial lawmaker on January 26.

The city is located close to south Waziristan tribal region and Bannu and Tank districts of the North West Frontier Province, where the Pakistani Taliban [Images] have a strong presence.