Four people were killed and over two dozen wounded, most of them police officials, in a suicide car-bomb attack on a police station in northwest Pakistan on Saturday, officials said.
"The attacker detonated his pick-up van at the gate of the main police station in Karak town" in North-West Frontier Province, local police chief Sajid Mohmand told AFP.
"Two policemen were killed on the spot and two civilians later succumbed to their injuries in the hospital," he added.
At least 26 people were wounded, including 21 policemen, two of whom were in a "critical" condition.
"It was a powerful blast, at least six rooms were demolished," local administration chief Ajmal Khan said, adding that one bus and two police vehicles were damaged.
A nearby mosque and five houses were also damaged, he said.
Karak lies 150 kilometres (94 miles) southeast of Peshawar, the capital of North West Frontier Province, which has been plagued by militant violence, including bomb attacks blamed on Taliban and Al-Qaeda-linked insurgents.
The attack came as thousands of Muslims staged rallies across the country to celebrate Eid Milad-un-Nabi, which marks the Prophet Mohammed's birthday, despite security fears.
Elsewhere, in the northwestern district of Dera Ismail Khan, gunman opened fire on an Eid Milad un-Nabi procession, killing one man and wounding several others, officials said.
The attack in Karak follows a clash in the nearby garrison city of Kohat on Friday in which Pakistan security forces killed 17 militants, officials said.
Pakistan's military has launched a number of offensives against Islamist militants in the tribal belt where the United States says Al-Qaeda has carved out its headquarters in the most dangerous terrain on Earth.
Pakistan is under increasing US pressure to do more to act against militants who stage cross border attacks in Afghanistan against NATO and US forces fighting an eight-year war against the Taliban.
More than 3,000 people have been killed in suicide and bomb attacks across Pakistan since July 2007 in a deadly campaign blamed on Islamist militants opposed to the government's alliance with the United States.
In the attack on the religious procession in Dera Ismail Khan district, police said, two or three armed men hiding behind the trees opened fire on hundreds of people carrying banners and reciting hymns.
Senior police officer Bashar Khan said rally in the district's Dhaki More neighbourhood was organised by a Sunni Muslim party. No arrests were reported.
Khan said seven participants in the rally were wounded in the attack, one of whom died in hospital. Health officials confirmed the casualties.
Officials refused to speculate who could be behind the attack. The town has been hit frequently by sectarian violence and extremist attacks.
"Dera Ismail Khan has been target of both militant attacks and sectarian violence," local police chief Gul Afzal Afridi told AFP.
"We cannot immediately blame any group, we are investigating," he said.
Firing also took place on a religious rally in the industrial city of Faisalabad, in central Punjab province, where four marchers were wounded.
An angry mob attacked a nearby police station and torched dozens of motorbikes and private cars, police said.
Shiites account for about 20 percent of Pakistan's Sunni-dominated population of 167 million. Although the two communities usually coexist peacefully, more than 4,000 people have died in outbreaks of sectarian violence since the late 1980s.