Snipers firing from rooftops and a cemetery killed at least 17 people in a series of attacks yesterday on a Shi'ite religious procession in Baghdad attended by hundreds of thousands of pilgrims, officials said.

They said four gunmen were also killed and at least 253 people injured, most of them slightly when they fell while fleeing the gunfire.

The "terrorist assaults" took place when the pilgrims were walking through Sunni areas on their way to the shrine of Imam Moussa Kadhim, an 8th century saint, Health Ministry spokesman Qassim Allawi said.

In one neighborhood, security forces and Shi'ite militiamen in flak jackets exchanged gunfire with unseen assailants who were firing from houses and buildings.

Some attackers fired from behind tombstones in a Sunni cemetery.

The violence was not unexpected given the cycle of tit-for-tat attacks by Shi'ites and Sunnis in Iraq since the bombing of a Shi'ite mosque on February 22. The sectarian warfare, along with the equally deadly Sunni Arab insurgency, has become the biggest challenge for the unity national government and its ally, the United States.

Interior Ministry spokesman Col. Saddoun Abu al-Ula said 17 pilgrims were killed and 253 injured during the attacks. Only a few of the injured sustained gunshot wounds while the rest suffered injuries in falls while running in panic, he said.

"We are responsible to make this work, despite these challenges," he said. Scores of militants were arrested, including some of those who fired on the pilgrims and others who were planning to, he added.

Police said four militants including two snipers were killed.

The violence occurred despite thousands of troops being deployed and the government imposing a ban on private vehicles from Friday night until Monday morning to prevent car bomb attacks.

Last year, the government said about 1,000 people died during the Imam Kadhim commemoration when rumors of suicide bombers triggered a mass stampede on a bridge across the Tigris River.

(China Daily via agencies August 21, 2006)