Islamabad, Pakistan (CNN) -- Thirty people were killed and more than 50 others were wounded Monday in a suicide blast targeting a Shiite procession in Pakistan's financial capital of Karachi, officials said.

Fifteen of those injured were in critical condition, Sagheer Ahmed, minister of health for Sindh province, told CNN.

The blast took place on M.A. Jinnah Road where thousands of Shiite devotees were commemorating Ashura, a major religious observance, said police Inspector Mahmood Ahmed.

Ashura marks the death anniversary of Imam Hussein, grandson of Prophet Mohammed. Hussein, who was killed in battle in Karbala in 680 A.D., is regarded as a martyr -- and the battle is one of the events that helped create the schism between Sunnis and Shiites, the two main Muslim religious movements.

Religious mourning during Ashura is characterized by people chanting, beating their breasts in penance, cutting themselves with daggers or swords and whipping themselves in synchronized moves.

Shias are a minority in Pakistan.

A day earlier, a suicide bomber blew himself up at the entrance to a mosque in Muzaffarabad in northeast Pakistan.

Three police officers and four civilians died in the blast. Eighty-one others were wounded.

CNN's Pierre Bairin contributed to this report.