Three gunmen attacked a Shiite mosque in Quetta, Pakistan, on Friday, killing 31 worshippers and injuring 30.
The toll is likely to go up, Information Minister Sheikh Rashid Ahmed said in Islamabad.
The attack triggered riots in Quetta, the capital of the southwestern Baluchistan province, as the Hazara community, which was targeted, took to streets and burnt vehicles and shops.
Army was called to assist the civil administration in maintaining law and order and curfew was imposed.
Local police officials said the gunmen exploded a bomb and fired on hundreds of people who had gathered for Friday prayers at the mosque on Mc Coughly Road.
A police official was quoted as saying that one of the attackers was killed and another captured.
No one claimed responsibility for the attack although the police suspected the hand of the Sipha-e-Sebha, a banned Sunni extremist outfit.
At least 12 police recruits, belonging to the Hazara community, were shot dead in Quetta last month.
President Pervez Musharraf, who is in Paris, condemned the attacks and asked the authorities to beef up security.
"It is unfortunate that there are some elements who strive to undermine whatever Pakistan stands for, whatever vast majority of Pakistan stands for," he said.
Prime Minister Mir Zafarullah Khan Jamali, who hails from Baluchistan, was in Quetta in the morning to attend various public functions. He was staying put there to coordinate relief efforts.