At least 30 have now died in five attacks on Shiites claimed by the Pakistani Taliban over the past five days, while about 100 were wounded in the run up to the holiday, which commemorates the 7th century death of the Prophet Muhammad's grandson. The schism between Sunni and Shiite Muslims dates back to that time.
Sunday's explosion went off as hundreds of Shiites were passing through the main intersection of the city of Dera Ismail Khan, area police official Abdul Sattar said. An initial investigation suggested a bomb was planted near a shop along the procession route, he added.
Several of injured are in serious condition, said local hospital official Dr. Faridullah Mahsud, adding that three members of a paramilitary unit providing security were among the injured. Mahsud confirmed the five deaths.
The Pakistani Taliban, a Sunni extremist group, frequently attacks Shiites, who they consider heretics. Ashoura ceremonies are a prime targets, since they draw large crowds that march in processions to mourn the martyred Imam Hussein.
Qais Abbas, a Shiite survivor, said the procession was in the Chogla intersection of the city when the bomb went off. One of his relatives was in critical condition, he said, but he and others were moving the wounded to other hospitals that were better equipped.
"Here we are not getting proper care for them, there are not enough doctors or medicines," he said.
The same city was hit by a similar bombing on Saturday, which killed seven and injured 30. On Wednesday night, a Taliban suicide bomber struck a Shiite Muslim procession in Rawalpindi, a garrison city near Islamabad, killing 17 people. Also Wednesday, the Taliban set off two bombs outside a Shiite mosque in the southern city of Karachi, killing one person and wounding 15 others. Pakistani Taliban have claimed responsibility for all the attacks, with spokesman Ehasanullah Ehsan saying by telephone that the group will not relent and "looks forward to more ahead."
Authorities have deployed thousands of additional police across the country to beef up security for the holy day. Mobile phone service has been shut down in all the major cities to prevent such bombings, which officials say often use cellular phones as remote detonators.