KARACHI, 1 June 2004 — A bomb ripped through a Shiite mosque in Karachi yesterday, killing at least 15 people and wounding more than 35. The bomb went off at the Imambargah Ali Raza mosque on M.A. Jinnah Road during Maghreb prayers.

A senior official said the attack was possible retaliation for the assassination of a senior Sunni cleric in the city on Sunday.

"I heard a big explosion, followed by flames from the front of the mosque and I saw two injured people falling on the road, bleeding, and one had no legs," said Ghulam Hussain, a fruit vendor, who witnessed the blast from about 200 meters away.

Tariq Jamil, chief of operations of Karachi police, said it was a "high-intensity bomb" and at least 15 people were killed and more than 35 injured.

Most of the casualties were taken to three hospitals in private vehicles. Other bodies were retrieved from the debris and ferried off in ambulances.

Ali Abbas, a young worshipper at the mosque, was pushing people out of the area, saying there was an abandoned bag in the mosque and he was afraid it contained another bomb, but inside people were still gathering up human flesh.

Bomb disposal experts later arrived and took the bag away.

Information Minister Sheikh Rashid Ahmed said President Gen. Pervez Musharraf had expressed grief over the killings and would take an "important step" in response to the incident, but did not elaborate.

The bombing triggered riots. Hundreds of Shiite youths set fire to two police vehicles and a gas station outside the mosque, and then ransacked two government offices, stealing furniture and torching it at a traffic intersection.

Police fired tear gas, trying to disperse the mob. Six or seven gunshots were heard, but it was not clear who fired them.

Interior Ministry spokesman Abdur Rauf Chaudhry said it was "too early" to say who was behind the attack, but said "it appears to be sectarian" violence.

On Sunday, unidentified gunmen assassinated a senior Sunni cleric Nizamuddin Shamzai, triggering riots across Karachi and stoking fears of sectarian violence between Sunnis and Shiites.

The blast "could be a reaction to yesterday's incident," Chaudhry told The Associated Press in the capital Islamabad.

The worst damage from the blast appeared to be in the area where people wash up before praying. The dome of mosque was broken.

The explosion shattered windows in a tall building opposite the mosque, leaving shards of glass scattered on the asphalt.

Jamil said it was not immediately clear if it was a suicide attack, saying that police were unable to gain access to the mosque because of the crowd. He said a vehicle belonging to a bomb disposal squad was among the those destroyed by rioters.

Saqlain Raza, a worshipper who was parking his motorcycle outside when the blast occurred, estimated that about 30 to 35 people were inside the mosque at the time. "I fell down and the motorbike fell on me. I pushed away the bike and tried to run, and I started hearing screaming people so I rushed inside. One three-year old child was bleeding from the head and stomach. I carried the boy out and a car took him to hospital," Saqlain said.

Karachi has been the scene of recent sectarian violence and terrorist attacks, including twin car bombings near the US consul's residence last week.

- Additional input from AP