Tens of thousands of supporters of defeated presidential candidate Mir Hossein Mousavi gathered in downtown Tehran on Wednesday for a fifth day of protests against last week's election result, witnesses said.
Meanwhile, Mousavi and former Iranian President Mohammad Khatami called on authorities to release from custody all protestors in the post-election riots in Iran.
Dozens of reformists have been arrested since the nationwide elections in the country, and 29 are believed to have been killed in clashes with security forces.
Mousavi called for a day of mourning for those killed in the clashes set off by a disputed presidential election.
Mainly dressed in black and also wearing wristbands and headbands in Mousavi's green campaign colors, they assembled in Haft-e Tir square and streets around it, the witnesses said. Most of the protesters were silent and making victory signs.
One street leading to the square was packed for several kilometers, witnesses said.
At least one young woman held a picture of one of those killed during post-election violence that has rocked Iran since official results of the election were announced Saturday, showing Ahmadinejad had won by a landslide against Mousavi.
Mousavi supporters in Tehran, Tuesday (Photo: Hamed Saver)
"A number of our countrymen were wounded or martyred," Mousavi said on his website, calling Thursday's day of mourning. "I ask the people to express their solidarity with the families ... by coming together in mosques or taking part in peaceful demonstrations."
Mousavi and his backers say the election was rigged. The authorities deny it. Fars News Agency earlier quoted Interior Minister Sadeq Mahsouli as saying "no permission has been issued for a gathering or rally in Haft-e Tir Square" Wednesday.
One witness said police were blocking traffic on one road leading to the square.
As in previous pro-Mousavi rallies, demonstrators held pictures of him as well as green balloons, witnesses said.
Dudi Cohen contributed to this report