Thousands of Iranians had gathered in several squares in Tehran by midday Monday, heeding calls in recent days by opposition leaders to demonstrate in solidarity with Egyptian and Tunisian protesters, who have recently toppled their regimes, The Wall Street Journal reports.

About 4,000 people had gathered in Azadi Square, in central Tehran, and more were streaming in, with dozens of police on motorbikes circling the square, according to eyewitnesses, opposition websites and Internet posts. Witnesses said a few thousand protesters had also gathered in Imam Hussein square, sitting on the ground and breaking out in chants when police tried to disperse them.

Security forces in the streets appear to be uniformed police, so far, according to eyewitnesses. In past demonstrations, plain-clothes security officers, including the Basij paramilitary, have been deployed. Early Monday, they hadn't been reported by eyewitnesses.

Opposition leaders Mir Hossein Mousavi and Mehdi Karoubi had been placed under house arrest early Monday, with communication lines to their home and mobile phones cut off, according to opposition websites. Police cars blocked the entry to their streets and, at one point, prevented Mr. Mousavi's wife from leaving her house.

Read the entire story at wsj.com