Police in Karachi used tear gas to break up crowds of Shi'ites who took to the streets on Friday to protest the killing of a prominent Shi'ite cleric.
Allama Hasan Turabi died of wounds suffered in a suicide bombing outside his Karachi home. Authorities say his nephew and the bomber died in the blast on Friday.
Following Turabi's death, city authorities deployed police and paramilitary forces to prevent a sectarian backlash. But hundreds of Shi'ites took to the streets, throwing rocks and chanting religious hymns and anti-American slogans.
Turabi escaped an assassination attempt in April. He was getting into his car at the time of the blast.
There has been no claim of responsibility for the attack. But authorities have recovered the bomber's remains and hope it will lead to quick identification and possible links to the attack.