Iranian police have placed opposition leader Mir Hossein Mousavi under house arrest, his official website says.
It says the move is intended to block him from attending a rally in Tehran in support of the protests in Egypt.
It is the latest in a series of arrests of people linked to Mr Mousavi and fellow opposition leader Mehdi Karroubi, also under house arrest.
Several opposition groups have vowed to take part in the protest, although officials have banned the gathering.
Although Iran's establishment officially supports the Egyptian popular protests, it says the rallies are a "political move" by the two opposition leaders.
The authorities have stepped up security in the capital, blocked access to internet sites, and started jamming satellite news channels.
Analysts say Tehran is trying to stop opposition groups from using the Egypt rally as a means to re-ignite anti-government protests - last seen in 2009 - against the disputed re-election of President Mahmoud Ahmadinejad.>>>
|نسرین ستوده: زندانی روز||Dec 04|
|Saeed Malekpour: Prisoner of the day||Lawyer says death sentence suspended||Dec 03|
|Majid Tavakoli: Prisoner of the day||Iterview with mother||Dec 02|
|احسان نراقی: جامعه شناس و نویسنده ۱۳۰۵-۱۳۹۱||Dec 02|
|Nasrin Sotoudeh: Prisoner of the day||46 days on hunger strike||Dec 01|
|Nasrin Sotoudeh: Graffiti||In Barcelona||Nov 30|
|گوهر عشقی: مادر ستار بهشتی||Nov 30|
|Abdollah Momeni: Prisoner of the day||Activist denied leave and family visits for 1.5 years||Nov 30|
|محمد کلالی: یکی از حمله کنندگان به سفارت ایران در برلین||Nov 29|
|Habibollah Golparipour: Prisoner of the day||Kurdish Activist on Death Row||Nov 28|