Gunmen opened fire on Shi'ite pilgrims in southern Baghdad on Sunday, killing seven of them as thousands of worshippers made their way to a revered shrine in the Iraqi capital, police said.

Iraqi forces have tightened security around the Kadhamiya district in northwestern Baghdad ahead of a major Shi'ite religious pilgrimage this week, an army spokesman said.

Police said the pilgrims who were killed were on foot. It appears they had come from cities in southern Iraq, which is predominantly Shi'ite.

Shi'ite pilgrims have often been the target of Sunni Islamist al Qaeda militants who consider Shi'ism - the majority Muslim denomination in Iraq - heretical.

But recent Shi'ite religious events have passed relatively peacefully as violence in Iraq has dropped to four-year lows. The annual pilgrimage to the Kadhamiya area, location of a revered shrine, was expected to attract more pilgrims than usual because of better security, major-general Qassim Moussawi, spokesman for Iraqi forces in Baghdad, said.

"We expect at least a million [people], definitely multiples of last year," Moussawi told a news conference before reports emerged of the shooting of the seven pilgrims. Thousands of pilgrims have already entered Baghdad for the event, which peaks on Tuesday.

The pilgrimage marks the death of one of Shi'ite Islam's 12 imams. The Kadhamiya pilgrimage was marred in 2005 by one of the worst losses of life in a single incident since the 2003 US -led invasion, when rumours of a bomb attack triggered a stampede among pilgrims crossing a bridge leading to the shrine.

Up to 1,000 people were killed. The bridge has since remained closed, but is expected to be reopened soon after this year's pilgrimage. Other bridges and roads leading to Kadhamiya have been closed for the event, and a vehicle curfew would be imposed, Moussawi said.

Security forces deployed for the event include a team of female guards to search women. Women have carried out numerous suicide attacks in recent months, many in northeastern Diyala province.

The Kadhamiya pilgrimage is one of several religious events in the Shi'ite calendar, which have attracted millions since the fall of former Iraqi President Saddam Hussein. The Sunni leader restricted participation in the events.

In other violence, a bomb wounded a member of an Iraqi provincial council and killed two of his bodyguards in the city of Falluja on Sunday, in what police said was an assassination attempt.

Zeki al-Mohammedi, a member of the Anbar provincial council and head of the Falluja branch of the Iraqi Islamic Party, escaped with minor wounds when the bomb exploded inside the garage of his home. - Reuters