The drive-by shooting occurred early Friday in Zubair, some 20km southwest of the mainly Shia southern city of Basra, according to a spokesman for the Iraqi Islamic Party, the main Sunni group.

The attack fuelled fears of a new round of tit-for-tat sectarian killings between majority Shias, who control the government, and Sunni Arabs, dominant under ousted dictator Saddam Hussein and who today provide the backbone to the current insurgency.

Top government officials have blamed insurgents for triggering Wednesday's mass stampede on a Baghdad bridge, which led to nearly 1,000 Shia pilgrims being trampled to death or drowning in the Tigris River. Over 800 were wounded.

Hundreds of thousands of Shias had descended upon the Baghdad neighbourhood of Kadhmiya for a religious commemoration, crowding the bridge which was bottlenecked by tight security measures aimed at vetting pilgrims.

Shouts claiming that suicide bombers were present in the crowd sent panicked pilgrims -- many of them women and children -- stampeding in every direction.

Suicide bombings are usually blamed on the insurgency and Sunni extremists foreigners, who infiltrate into Iraq seeking a battleground with the West, and with Shias, whom they perceive as heretics.