Chanting slogans against Afghanistan's ousted Taliban and an extremist Sunni Muslim Pakistani leader, more than 1,000 people rallied in the capital Islamabad to protest the attack on a mosque last week that left at least 50 Shiite Muslims dead.
"We strongly condemn this tragedy," read a sign carried by some protesters as they marched from a main Shiite mosque to a busy intersection in Islamabad's main commercial district.
About 100 armed policemen blocked off the thoroughfare, and kept an eye on the rally, which ended peacefully.
Three men attacked the Shiite mosque in the southwestern city of Quetta last Friday. Two of the attackers were killed while the third assailant blew himself up inside the mosque.
No one has claimed responsibility for the attack.
Shiite leaders said the attackers were not Pakistanis. Police and intelligence agencies are investigating the possibility that Taliban and al-Qaeda fugitives may have been behind the attack.
Friday's demonstrators believed pro-Taliban elements were behind the assault. Many of the victims were ethnic Hazaras. The Taliban, who were ousted in 2001, were suspected of persecuting Afghanistan's Hazara ethnic group.
"Death to the Taliban mentality," the protesters chanted.
The demonstrators also denounced Maulana Azam Tariq, who headed the outlawed Sunni militant group Sipah-e-Sahaba. Tariq is now a government ally after winning a parliamentary seat as an independent candidate.
The group has been blamed for involvement in the killing of hundreds of Shiites in Pakistan. Extremist Sunni groups have been blamed for attacks in the past against Shiites, who are a minority in Pakistan.
While most Sunni and Shiite Muslims live in peace, small extremist groups from the two communities have been blamed for attacking each other.
Rivalry between Sunnis and Shiites dates back to the seventh century, when they split on the issue of succession to Islam's Prophet Mohammed following his death.
Separately, an alliance of mainly Sunni religious groups declared Friday a day of mourning over the Quetta mosque attack and asked worshippers to pray for the victims.