Since Wednesday, at least 31 have been killed in bombings aimed at Pakistani Shiites and claimed by the Taliban, who espouse an extremist interpretation of Sunni Islam. Over 100 were wounded in the attacks during the run-up to the holiday, which commemorates the 7th century death of the Prophet Muhammad's grandson. The schism between Sunnis and Shiites 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, police said, where food and water stalls were set up to serve the crowd. An initial investigation suggested a bomb was planted near a shop along the procession route.
"The bomb contained about eight kilograms of explosives and steel balls, and was detonated with a remote control device," city police chief Sohail Khalid said.
Several of injured are in serious condition, said Dr. Faridullah Mahsud, an official at the city's hospital, who added that three members of a paramilitary unit providing security for the procession were among the injured. Dr. Khalid Aziz, the top official at the hospital, put the death toll at six.
The Pakistani Taliban frequently attack 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. Early in the day, participants beat their chests in grief over Hussein's killing, while later some cut themselves to express their sorrow in blood.
Qais Abbas, a Shiite survivor, said that one of his relatives was in critical condition, but that 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.
After the blast, thousands of Shiite mourners staged a sit-in at a nearby intersection, refusing to move unless assured quick and stern action against the perpetrators. The procession has now been attacked for a second consecutive day.
A similar bombing killed seven and injured 30 from the group a day earlier, and last week attacks on Ashoura observers took place elsewhere in the country. On Wednesday night, a Taliban suicide bomber struck a Shiite procession in Rawalpindi, a garrison city near the capital, Islamabad, killing 17. Earlier that same day, 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 on Sunday 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.