Iran has flooded Tehran with police and militia to crush any pro-Egypt marches it fears could turn into anti-government demonstrations.
The security clampdown was similar to the backlash that crushed a wave of protests after the disputed re-election of Mahmoud Ahmadinejad in June 2009.
But opposition supporters revived a tactic from the unrest, shouting "Allahu Akbar," or God is Great, from rooftops and balconies into the early hours in a sign of defiance toward Iran's leadership.
The reformist website kaleme.com said police put officers in front of the home of leading activists Mir Hossein Mousavi ahead of the planned demonstration in central Tehran.
Mr Mousavi and fellow opposition leader Mahdi Karroubi have been under house arrest since last week after they asked the government for permission to hold a rally in support of the uprisings in Egypt and Tunisia.
The government rejected the request and warned of repercussions if demonstrations took place.
On Sunday the opposition renewed its call to supporters to rally, and accused the government of hypocrisy by voicing support for the Egyptian and Tunisian uprisings while refusing to allow Iranian political activists to stage a peaceful demonstration.
The uprising in Egypt opened a rare chance for the political gambit by Iran's opposition. Several opposition activists and aides to Mr Mousavi and Mr Karroubi have been arrested as part of government efforts to intimidate the opposition and undermine its resolve to hold a rally.
Mr Ahmadinejad claimed the Egyptians who toppled president Hosni Mubarak took inspiration from Iran's 1979 Islamic Revolution, which brought down a Western-backed monarchy.
Iran's opposition movement used the comments to push the government into a corner and request permission to march in support of Egypt's protesters. Iranian officials quickly back pedalled and said no pro-Egypt rallies were allowed - bringing sharp criticism from the White House and others.