Scores of Iranian security forces were on the streets of Tehran on Monday to prevent a planned opposition rally in solidarity with popular uprisings in Egypt and Tunisia that toppled their presidents, witnesses said.

Iranian authorities refused a request by opposition leaders Mirhossein Mousavi and Mehdi Karroubi to stage the rally for fear of a revival of anti-government mass protests that shook the country after a disputed presidential vote in 2009.

Defying the ban, the opposition nevertheless renewed the call for the rally. Iran's authorities have warned the opposition to avoid creating a "security crisis" by reviving mass anti-government protests that erupted after the vote, the biggest unrest in Iran since the 1979 revolution.

"There are dozens of police and security forces in the Vali-ye Asr Avenue ... they have blocked entrances of metro stations in the area," a witness told Reuters by telephone,
referring to a large thoroughfare that cuts through Tehran.

Another witness said police cars with windows covered by black curtains were parked near Tehran's notorious Evin prison.

Mousavi's website Kaleme said security forces had set up a road block, refusing access to the opposition leader's residence in southern Tehran. The site also said both mobile and landline telephone communications with Mousavi's house were cut as well.

"It seems these newly-set restrictions are aimed at preventing Mousavi and his wife (Zahra Rahnavard) from attending the rally," Kaleme said. Plain-clothes police stopped Rahnavard leaving the house, another opposition website reported.

Iranian Supreme Leader Ayatollah Ali Khamenei called the uprisings in Egypt and Tunisia an "Islamic awakening", akin to the 1979 revolution that overthrew the U.S.-backed shah.

The opposition, however, saw the uprisings as being more similar to their own protests following the June, 2009 election which they say was rigged in favor of President Mahmoud Ahmadinejad.

Revolutionary Guards, fiercely loyal to Khamenei, put down the 2009 protests. Two people were hanged and scores of opposition supporters jailed. The last mass demonstration was held in December of 2009 when eight people were killed.

Iranian state television repeatedly showed footage of a state-organized rally on Friday to mark the 32nd anniversary of the 1979 revolution. But cries of "Allahu Akbar" (God is Greatest) were heard from rooftops overnight, a move urged by the opposition copying tactics used by revolutionaries in 1979.

Authorities deny rigging the 2009 election and accuse opposition leaders of being part of a Western plot to overthrow the Islamic system.

"They are incapable of doing a damn thing," the hardline Kayhan newspaper quoted Intelligence Minister Heidar Moslehi as saying, echoing words used by revolutionary leader Ayatollah Ruhollah Khomeini to refer to the United States.

The opposition is "guided by Iran's enemies abroad", Moslehi said.

Mousavi says the freedom movement is alive, but his campaign is fading as many Iranians feel the former prime minister lacks the courage to confront the establishment from which he sprang.

The opposition denies having any links to the enemies abroad.

Many Iranians critical of the government now seem unwilling to risk violence or arrest with displays of dissent. But the opposition's call has gained momentum on social networking websites, with more than 56,000 people pledging to participate on one protest group's Facebook page.