More than 180 Hazara Shia have been killed since January in what they say is an atmosphere of impunity and hatred.
At least 22 people have been killed during a procession to mark a Shia religious holiday in the Pakistani province of Sindh.
The blast on Friday, which struck worshippers marking Ashoura in the city of Jacobabad, also left 30 people wounded.
A police official told the AFP news agency that the procession was targeted by a suicide bomber.
Al Jazeera’s Kamal Hyder, reporting from Pakistan’s capital Islamabad, said more than 10,000 extra police officers had been deployed to guard Shia processions during Ashoura.
No one immediately took responsibility for Friday’s bombing, but an armed group, Lashkar-e-Jhangvi, had claimed responsibility for Thursday’s attack and threatened more violence against Shia.
A suicide bombing at a Shia mosque in the southwestern province of Balochistan on Thursday killed at least 10 people.
Pakistan’s Shia minority, who make up about 20 percent of the total population, are frequently targeted by hardline Sunni groups, including the Pakistani Taliban.
The armed groups consider Shia adherents to be heretics and have demanded the government stops classifying them as Muslims.
In January, at least 49 people were killed in an explosion during Friday prayers at a mosque in Shikarpur, also in Sindh province.
Ashoura marks the anniversary of the death of the Prophet Muhammad’s grandson, Hussein, who was killed at the battle of Karbala more than 1,300 years go.
Shia Muslims consider it a day of mourning and mark the day with processions and re-enactments of his death.