Pakistani President Pervez Musharraf has vowed to punish those responsible for today's (Tuesday's) attack on Shi'ite Muslims in the southwestern city of Quetta that killed at least 41 people.
Pakistani officials said 150 people were also wounded when gunmen attacked a group of Shi'ites holding a religious procession for Ashura. Officials said five of those killed were policemen. They also said there was an explosion heard in the area during the attack.
Shi'ite Muslims went on a rampage following the assault and burned a number of shops. Authorities have since imposed a curfew in Quetta, and have called in troops to patrol the city.
U.N. Secretary General Kofi Annan has condemned the attack, saying he was appalled by the cowardly act. European Union policy chief Javier Solana has also condemned the assault.
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.