A bomb attack on a Shiite Muslim procession killed three people and wounded more than 50 in northwest Pakistan on Sunday as Shiites marked their holiest day Ashura, police said.

The bomb exploded in the city of Dera Ismail Khan in Khyber Pakhtunkhwa province, where a blast on Saturday killed eight people near a Shiite Muslim procession.

"Three people have been killed and more than 50 injured. The target of the attack was the Ashura procession," police official Anwar Khan Akbar told AFP.

Nazir Khan, a second police official in the city, said the bomb was planted inside a shop. "It was a remote-controlled bomb and exploded as a procession reached here," he said.

Khalid Aziz, a doctor in the city's main hospital, told Pakistan's private ARY TV channel the condition of some of the injured was critical.

Pakistan has deployed tens of thousands of police and paramilitary forces to try to avert sectarian clashes or attacks on Ashura processions, when Shiites whip themselves to mourn the seventh-century killing of the Prophet Mohammed's grandson Imam Hussein.

Authorities have ordered heightened security, with services for mobile phones -- which are often used to trigger bombs -- suspended in major cities.

Shiites, a minority in Sunni-dominated Pakistan, have been marking the holy month of Muharram which culminated Sunday in Ashura.

The Pakistani Taliban claimed responsibility for Saturday's attack.

It also claimed a suicide attack that killed 23 people last Thursday at a Shiite procession in the garrison city of Rawalpindi.