A crowd hurling shoes, rocks and tomatoes forced former Prime Minister Iyad Allawi to cut short a visit on Sunday to Iraq's holiest Shi'ite shrine during a campaign trip to the city of Najaf, police officers said.

A spokeswoman for Allawi, a secular Shi'ite, said she had no information on the incident but confirmed that Allawi, who is challenging the ruling Shi'ite Islamist Alliance bloc at next week's parliamentary election, had been in Najaf during the day.

A police captain, speaking on condition of anonymity, said a large crowd of worshippers at the Imam Ali mosque hurled sandals and shoes at Allawi -- a grave insult in Iraqi culture.

A second police officer said some of Allawi's bodyguards fired in the air to disperse the crowd and that also threw rocks, sticks, tomatoes and other projectiles. Police also intervened to break up the disturbance, he said.

Both policemen said they believed supporters of militant cleric Moqtada al-Sadr were responsible for the disturbances, though evidence for this was unclear.

"When Allawi entered the shrine, a few people, believed to be Sadrists picked up batons and threatened to attack him," the police captain said at the scene after the incident.

"His American and Iraqi guards fired in the air when everyone started throwing shoes and sandals at him."