A roadside bomb in the city of Dera Ismail Khan struck a religious procession Saturday, killing at least seven and wounding 30, according to the BBC.
"The explosion was powerful and was heard many kilometers away," police officer Siddiq Khan told AFP news.
Reuters reported from the scene:
"The explosion was so powerful that it hurled a young boy onto a rooftop from a street, where a man later carried away half of his body, as a policeman with a bomb detector and residents stood near blood stains."
Reports say a 10 kilogram bomb with ball bearings was planted in a dustbin and triggered by remote control as a line of Shiite Muslims, a minority group in Pakistan, readied to observe Ashoura on Sunday. Ashoura commemorates the death of Imam Hussein, Prophet Muhammad's grandson.
Pakistan President Asif Ali Zardari condemned the attack.
"Such nefarious acts cannot deter the people and the government in their fight against the scourge of militancy," he said in a statement.
Dera Ismail Khan is a well-known center of Al Qaeda-linked militants.
Prior to the bombing, the BBC notes, more than a dozen people had died in recent attacks.
More sectarian violence is threatened in Islamabad, Karachi and Quetta, Al Jazeera reports. As a precaution, Pakistan mobilized thousands of additional policemen, and in some cities canceled phone service, as bombs are often detonated via mobile phone.
The attacks, Al Jazeera says, are led by a terrorist organization known as Lashkar-e-Jhangvi - a group that hopes to destabilize Pakistan and establish a Sunni theocracy in the state.