No one has yet claimed responsibility for the blast, but authorities generally blame Sunni Muslim groups for such attacks.

'Considerable anger'

Al Jazeera's Kamal Hyder, reporting from Islamabad, said: "The attack angered a lot of people, they vented their anger on the police station this morning. [Police] were unable to provide security to these people in the procession. So there was considerable anger at police."

A blast on a main road from Pakistan to Afghanistan wounded six people[AFP]

Shia Muslims are observing the last week of a 40-day mourning period to commemorate the death of Hussein, the grandson of Prophet Muhammad, who was killed in 680 AD.

About 20 per cent of Pakistan's 160 million population are Shia Muslims.

"Security agencies had been warning in the past that some of the troubles are likely to spread into the sounthern part of Punjab because there has been a renewed wave of sectarian violence in certain areas," Hyder said.

"While that is a factor, the real concern is the escalation of suicide bombings."

Fighters killed

Also on Friday, security officials said that a massive ground and air offensive by government forces have killed 52 suspected anti-government fighters in the northwest Khyber region.

  

"Frontier Corp troops killed 52 militants, targeted five hideouts and destroyed an ammunition dump and eight vehicles in Chapri Feroze Khel in Khyber," a senior security official involved in the operation said.

  

The tolls were impossible to verify independently in the remote and dangerous region, where Pakistani troops are battling Taliban fighters to secure the Khyber for vehicles to carry supplies to Nato forces in Afghanistan.

There were also more violence elsewhere in the country on Friday.

A suicide bombing took place in the town of Jamrud on a key road between Pakistan and Afghanistan, wounding six people.

Overnight, a suicide bomber drove a car bomb into a police station in Mingora, the main town of northwest Swat Valley, where armed groups are fighting an armed campaign against the government.

Khaista Rehman, a local police station chief, said 11 security personnel were wounded, including seven policemen and four paramilitary soldiers.

The force of the explosion damaged dozens of shops and nearby buildings, but caused no other casualties, he said.