Meanwhile, Iranian exiles reported that Hezbollah has joined the security forces in suppressing the protests. Opposition groups claimed that as many as 1,500 Hezbollah operatives are taking part in clashes. Members of the terrorist organization, which reportedly receives training and aid from Iran, assisted the authorities to disperse the demonstration in Tehran’s Azadi Square last week.

Also Sunday, Iran arrested the daughter of former president Akbar Hashemi Rafsanjani for taking part in a banned opposition rally, the official IRNA news agency reported. Shortly thereafter, the semi-official Fars news agency reported she was released after being detained briefly.

“Faezeh Hashemi Rafsanjani was released after claiming that she was out shopping for cloths,” Fars reported.

Eye witnesses told opposition websites that security forces were trying to disperse the demonstrators using tear gas and live fire. An unofficial report said one man was killed during a protest in Theran’s Haft-e-Tir Square. A website affiliated with Iranian student unions also reported that live fire used by security forces left one man dead. Another report said that a protestor was killed in the Vanak square.

CNN reporter Reza Sayah tweeted that he saw security forces beating at least 15 people with batons in Tehran’s Revolution Square. He added that at least four protestors were arrested.

Farsi BBC reported shots were fired in Abbas Abad in north Tehran. Unofficial reports suggest that thousands of protestors clashed with security forces in Vali-Asr Square and called “Death to the dictator.”

Meanwhile, the pro-government Fars news agency said that “calm” prevailed in Tehran in the face of the presence of security forces in “full strength.”

“The police was in control of the situation and there was peace in the city with no reports of any incidents,” Fars said.

YouTube video shows demonstrators fleeing from police in Shiraz

Many websites blocked

Social network users reported that many websites were blocked Sunday including the Gmail service. Opposition website Rahesabz.net reported that the cell phone network in central Tehran had been cut off. Another report said that overseas calls to Tehran were also blocked in order to restrict the flow of information to foreign media outlets.

Earlier on Sunday, opposition activists gathered in several areas in Iran’s capital.

Iran warned the opposition on Saturday against staging demonstrations after calls were posted on websites for a rally on Sunday to commemorate two people killed during protests this week, state media reported.

Opposition leaders Mirhossein Mousavi’s and Mehdi Karoubi’s websites have called for nationwide rallies on Sunday, which they also said were intended to show “decisive support to the pro-reform movement and its leaders.”

Mousavi and Karoubi, who both lost to Ahmadinejad in the vote, have been placed under house arrest after calling for the rally.

AFP and Reuters contributed to this report