Protests come amid mourning in Pakistan after Shiite mosque bombing that killed 59 people

Pakistani protesters burn tires to condemn a blast at a Shiite mosque, Friday, Jan. 30, 2015 in Karachi, Pakistan. The bomb ripped through a mosque in Pakistan belonging to members of the Shiite minority sect of Islam just as worshippers were gathering for Friday prayers, killing dozens of people and wounding many others, officials said. (AP Photo/Fareed Khan) (The Associated Press)

Shiites across Pakistan are mourning and planning to protest after a bombing at a Shiite mosque in the country killed at least 59 people.

Abdul Qudoos Kalwar, a senior police official, says the death toll in the blast in Pakistan's Sindh province rose Saturday after three others died overnight from their wounds.

The bombing happened in Shikarpur, roughly 500 kilometers (310 miles) north of Pakistan's port city of Karachi. Another senior police official, Saqib Memon, also said Saturday that investigators believe a suicide bomber carried out Friday's attack.

Sunni Muslim extremists in Pakistan often target Shiites because they believe them to be heretics.

Shiites plan a mass funeral Saturday for the dead, as well as major protests in cities across the country.