An Iranian opposition website said violent clashes between security forces and opposition supporters were spreading in the country's capital on Saturday.

'Well-equipped security forces are clashing violently with the backers of opposition in many parts of downtown Tehran,' the Jaras website reported.

Police chief Esmail Ahmadi-Moqadam warned the pro-reform opposition of 'fierce' confrontation if it continued its 'illegal' activities, the semi-official Fars news agency reported.

The reformist Jaras website said many demonstrators were injured and arrests were made during clashes in the city of Isfahan, which occurred when Montazeri supporters gathered for the traditional third day of mourning for him.

'Police fired teargas to disperse people ... many people were injured ... some arrested,' Jaras said.

Another reformist website, Parlemannews, said at least 50 opposition backers, including four journalists, were arrested in Isfahan, one of Iran's biggest and most historic cities.

Security forces surrounded a mosque there to stop people entering, the Rah-e Sabz website said.

'Montazeri mourners shouted slogans against the top authorities,' it said. 'They are beating protesters, including women and children, with batons, chains and stones.'

Montazeri, who died on Saturday at the age of 87 in the holy city of Qom, was a fierce critic of the hardline clerical establishment who denounced President Mahmoud Ahmadinejad's re-election in June as fraudulent.

The authorities deny vote rigging charges and have portrayed the huge opposition protests that erupted after the poll as a foreign-backed bid to topple the Islamic establishment.

Despite scores of arrests and security crackdowns, opposition protests have repeatedly flared up since the vote.

'Hypocrites'

Referring to the city where Montazeri was born, Jaras said: 'Sporadic clashes started from Tuesday night in Najafabad and still continued. The situation is tense in the city. People are chanting anti-government slogans.'

In nearby Isfahan, Jaras said plainclothes security agents surrounded the house of a leading pro-reform cleric, Ayatollah Jalaleddin Taheri.

Police blocked streets in the area where the clashes took place and motorists honked horns to protest the security forces' treatment of demonstrators, Jaras said.

The reported incidents took place two days after huge crowds turned out in Qom for the funeral of Montazeri, when many people chanted anti-government slogans, websites said.

The opposition reports from Isfahan and Najafabad could not be verified independently because foreign media are banned from reporting directly on protests.

Government supporters staged counter rallies in Qom on Tuesday and Wednesday, condemning 'the insult against sanctities' during Montazeri's funeral procession, official media reported.

'This is the last time that something like that will happen in Qom. This is not a place for hypocrites,' Grand Ayatollah Hossein Nouri Hamedani told the crowd, state television said.

Iran's internal unrest, highlighted by Montazeri's arguments that the leadership had lost its legitimacy, has complicated the dispute over the Iranian nuclear programme, which the West believes may have military ends, not just civilian purposes.

Montazeri was an architect of the 1979 revolution that overthrew the U.S.-backed shah and was once named to succeed Ayatollah Ruhollah Khomeini as supreme leader.

But the man viewed as the spiritual patron of the opposition movement, fell from grace after criticising the mass execution of prisoners in the late 1980s.

Ahmadinejad's re-election, in the vote that losing opposition candidates said was rigged, kindled the biggest unrest in Iran's 30-year history and split the political and clerical establishment.

Montazeri's death occurred in the tense run-up to Ashura, on December 27, a politically important Shi'ite religious commemoration that offers the opposition another opportunity to show its strength.

Opposition backers have seized such occasions marked in the Islamic revolutionary calendar to raise their voices. – Reuters