By Jim Muir BBC Tehran correspondent

Thousands of conservative clerical students have staged a strike and demonstrations in the Iranian holy city of Qom in protest at a cartoon published in a reformist newspaper which they believe insulted the late leader of the Islamic revolution, Ayatollah Khomeini.

The newspaper has been suspended by a special court and three of its employees are reported to have been arrested.

Many thousands of conservative seminary students and their supporters marched through the streets of Qom chanting slogans denouncing the reformist newspaper which published the cartoon.

Religious colleges in Qom and elsewhere closed down for the day in what has become the latest round in the ongoing struggle between hardliners and reformists here.

Similarities to imam

The liberal paper which published the cartoon last week, Hayat-e No, had already announced that it was suspending publication for a few days to let the dust settle.

The current leader's brother is the newspaper's director

But it was later served with a temporary banning order issued by a special clerical court and three of its editors are reported to have been arrested.

In vain, the paper and its director have argued that the cartoon itself is 65 years old.

It shows a supreme court judge in America being squashed under the giant thumb of Franklin D Roosevelt.

The judge is elderly, bearded and wears a black robe, so the protestors say he looks like Ayatollah Khomeini and that this is therefore an insult to the late and much revered imam.

Ironically, the paper's director, Hadi Khamenei, is the reformist brother of the man who succeeded Ayatollah Khomeini as the country's supreme leader, Ayatollah Ali Khamenei.

He is normally identified with the conservative camp.

In an emotional speech to parliament, where he is a leading MP, Hadi Khamenei said he wished he had died in the Shah's jails rather than live to see the day when he would stand accused of insulting the imam.

Other leading reformists accused the hardliners of seizing on the cartoon to whip up religious sentiment.

They said they were trying to undermine two important reform bills currently before parliament and to discredit the reformists in advance of local elections at the end of next month.