TEHRAN (AFP) - Iranian police clashed with mourners at a memorial service Wednesday for dissident cleric Grand Ayatollah Hossein Ali Montazeri, arresting more than 50 and beating women and children, reports said. In early morning, hundreds of police and security force members surrounded the Seyed Mosque in Isfahan where the service was to be held and prevented mourners from entering, sparking fierce clashes, opposition websites said. The mourners were shouting slogans in support of Irans opposition Green Movement and police fired tear gas to disperse them, website Rahesabz.net said. Security forces are beating people including women and children with batons, chains and stones, it said, adding several have been arrested and many were injured. Parlemannews.ir, the website of Irans reformist minority faction in parliament, said over 50 people, including four reporters, were arrested in clashes. The latest crackdown on the opposition comes a day after its main leader Mir Hossein Mousavi was sacked from his post as president of the Academy of Art, which the architect and painter had headed for 10 years. Iranian authorities vowed to show no tolerance to protesters. We advise this particular movement to stop its actions or those who disturb order will be severely dealt with according to law, Irans police chief Esmail Ahmadi Moghaddam told the ISNA news agency. His deputy General Ahmad Reza Radan said police would crack down on any illegal gatherings during Ashura. If during illegal gatherings no red lines are crossed, then police will give a simple warning, Radan was quoted as saying by ISNA. But if they are crossed, police will intervene and could arrest people, he added, without specifying what constituted the red lines. An aide to supreme leader Ayatollah Ali Khamenei warned the regime would take action against opposition leaders in due time. Dealing with riot leaders has it own due time and we will act powerfully at the right time, Mojtaba Zolnoor was quoted as saying by the Fars news agency. Many hardliners have called for the arrest of Mousavi, who ran for president in June 12 polls which he lost to President Mahmoud Ahmadinejad amid claims the election was rigged, triggering sporadic protests ever since. Montazeri, who died aged 87 on Saturday, had been a bold supporter of the opposition, branding the government illegitimate and issuing blistering statements condemning violence by security forces against demonstrators. Once tipped to succeed the founder of the 1979 Islamic revolution, Ayatollah Ruhollah Khomeini, he had long been critical of the concentration of power in the hands of the supreme leader and called for constitutional changes to limit his authority. His funeral Monday in the holy city of Qom saw hundreds of thousands of mourners pour on to the streets, effectively turning the ceremony into a massive anti-government protest which ended in clashes with police. Wednesdays memorial service in Isfahan, where Montazeri had many followers, was to be led by prominent reformist cleric Ayatollah Jalaledin Taheri, whose house according to Rahesabz has been surrounded by security forces. Since Montazeris death, another prominent opposition supporter, Grand Ayatollah Yusuf Sanei, has faced pressure from hardliners, according to reformist website Norooznews.ir. It said that on Monday night about 1,000 members of Irans Basij militia attacked Saneis offices in Qom, breaking windows and beating up his staff. Regime loyalists have also held counter-protests in Qom and Isfahan in support of Khamenei. Mousavi, who still holds posts in a cultural body and an arbitration body, whose members are appointed by the supreme leader, was replaced by a conservative poet in his post at the Academy of Art. A prominent reformist MP, Dariush Ghanbari, branded his sacking as a political decision undoubtedly stemming from electoral grudges, Parlemannews reported.