Police in the Australian state of Victoria are investigating one of the country's most senior Islamic clerics after receiving complaints he incited his followers to attack gays.

At a prayer service to celebrate the conclusion of fasting for Ramadan held at the Albanian Mosque in Drummond St, Carlton, Rexhep Idrizi was alleged to have read from the Koran when he told his congregation of 1,000 that gays should have "their heads chopped off."

Idrizi, who is chairman of the Board of Imams, denied the charge and told the Sunday Herald Sun: "It's just spite from idiots."

"All I said was that homosexuality is prohibited in Islam," he said. "I wouldn't encourage anyone to attack my enemy. And if you put this in the paper, it's discrimination against Islam and we will defend ourselves."

He added that claims were unfounded and he had a video of the service at the mosque to prove it.

But a worshipper worshipper Asip Demiri, who was at the service, told the Sun that Imam Idrizi had verbally attacked gays. He said a complaint had been made to police and he urged others in the congregation to disavow the Imam's comments.

"I couldn't believe it. I was sitting there with my son and he comes out with comments as if the Koran says it's OK to attack homosexuals," Demiri said. "He told us they should have their heads chopped off.

"My son asked me if what the Imam said was true and I said 'No, it's not'. Then, he wanted to know if the Imam was lying and I couldn't give him an answer that would make any sense.

"We go there to pray, not to listen to that kind of rubbish. There were a lot of intelligent people there who were offended by it. He (Imam Idrizi) needs to be taken to task for it, because it gives Muslims a bad name."

Det Sgt Troy Burg confirmed police were investigating the complaint.

Last year, Imam Idrizi's son was jailed for four years and eight months, with a minimum of 15 months, for bashing three gay men.

Muhamed Idrizi, who was 19 at the time, and four others attacked, bashed and robbed a cyclist with a machete and two other men in two incidents on Feb 28 last year. The court heard that the group had gone on what he called a "puffter bashing" mission.

One victim was repeatedly kicked, punched and struck over the head with a machete in Alma Park, St Kilda. The gang then robbed the man, stripped him to his underwear and taunted him with homophobic epithets. They later robbed and attacked two other men in Elwood.

At the time, Imam Idrizi said his son had "been the devil this month."

"God will punish him," he said.

Victorian Gay and Lesbian Rights lobby convenor David McCarthy said his group would appeal to the Director of Public Prosecutions if police failed to fully investigate the allegations. Inciting violence is illegal under state law, which was recently expanded to include gays.