The authorities in Iran and Bahrain have stepped up security ahead of planned protests inspired by uprisings in Egypt and Tunisia.
Iranian police placed opposition leaders Mir Hossein Mousavi and Mehdi Karroubi under house arrest to stop them attending a rally in support of mass Egyptian protests that forced President Hosni Mubarak from power on Friday.
Access to several opposition Internet sites including Kaleme.com was blocked.
Thousands of people vowed to gather on Tehran's Azadi Square - the site of mass protests against the disputed re-election of President Mahmoud Ahmadinejad in 2009 - in defiance of an official ban.
"We definitely see them as enemies of the revolution and spies, and we will confront them with force," Revolutionary Guard Commander Hossein Hamedani told the state-run Islamic Republic News Agency.
In Bahrain, several people were injured in clashes ahead of a "Day of Rage" demonstration on Monday. There has been growing tension over the past six months between the ruling Sunni family and Bahrain's Shia majority, which complains of constant discrimination under the current regime.
"We call on all Bahraini people - men, women, boys and girls - to share in our rallies in a peaceful and civilized way to guarantee a stable and promising future for ourselves and our children," Bahraini activists said in a statement carried on Facebook and Twitter.
"We would like to stress that February 14 is only the beginning," the statement warned.
Thousands of people clashed with police in the Yemeni capital of Sanaa on Monday in a fourth day of anti-government protests demanding political reform and the resignation of President Ali Abdullah Saleh.
MOSCOW, February 14 (RIA Novosti)
