Pakistani President Pervez Musharraf has vowed to punish those responsible for Tuesday's attack on Shi'ite Muslims in the southwestern city of Quetta that killed 43 people, including six policemen.
General Musharraf ordered an investigation into the attack, which also left 150 people wounded, and promised compensation to the victims' families.
Pakistani officials say initial indications are that three men were involved in the attack. They say the assailants sprayed bullets into the crowd of Shi'ite worshippers and then detonated explosives strapped to their bodies. One of the attackers survived and has been detained.
Officials say a number of policemen are also being questioned in connection with the violence, which took place during a special Shi'ite religious observance, Ashura.
The violence occurred despite increased security throughout Pakistan for the Shi'ite commemorations, which have been marred by sectarian violence in the past.
Most of Pakistan's majority Sunni Muslims live peacefully with minority Shi'ites. But hundreds of people have been killed in the past in clashes between small radical groups from the two communities.