Iranian authorities said they would teach a lesson to rioters held in the worst unrest to befall the country since the 1979 Islamic Revolution.
(EDITORS' NOTE: Reuters and other foreign media are subject to Iranian restrictions on their ability to report, film or take pictures in Tehran.)
A moderate cleric defeated in this month's disputed elections called on Iranians to hold ceremonies on Thursday to mourn those killed at protests over the last week.
Trucks and police in riot gear were deployed on the main squares of Tehran on Tuesday, but there were no signs of any protest gatherings in the city by midday.
The Revolutionary Guard, loyal to the country's conservative religious establishment, have declared a crackdown on protests triggered by elections that gave President Mahmoud Ahmadinejad a landslide victory. Hundreds have been detained by police using tear gas and batons since results were published on June 13.
Those arrested in recent events will be dealt with in a way that will teach them a lesson, the official IRNA news agency quoted senior judiciary official Ebrahim Raisi as saying on state television late on Monday.
He said a special court was studying the cases.
The rioters should be dealt with in an exemplary way and the judiciary will do that, Raisi said.
Two losing candidates, ex-prime minister Mirhossein Mousavi and pro-reform cleric Mehdi Karoubi, accuse authorities of vote rigging and have demanded a rerun. But the top legislative body, the Guardian Council, ruled this out again on Tuesday.
The troubles have produced the first clear evidence of a public split in the clerical establishment between hardliners and those seeking more liberal policies.
An Iranian parliamentarian, Mahmoud Ahmadi, said on Tuesday Tehran would temporarily recall its ambassador to Britain, which the leading oil and gas producer has accused of fomenting trouble. A senior Iranian government source did not confirm the report carried by several Iranian news agencies.
Moderate cleric Mehdi Karoubi maintained pressure on authorities.
Karoubi calls on Iranians around the country to hold ceremonies on Thursday to remember those (killed) at protests, said aide Issa Saharkhiz.
The troubles have erupted against a background of tension between the West and Iran, a major factor in regional stability.
Tehran's hardline leadership is locked in dispute with Western powers over its nuclear programme, which it says is intended for power generation but which the West suspects could yield nuclear weapons that could destabilise the region.
State television said more than 450 people were detained during clashes with police in Tehran on Saturday in which at least 10 people were killed.
In New York, U.N. Secretary-General Ban Ki-moon urged an immediate stop to the use of force against civilians and said Iran should respect civil rights in dealing with protests.
People in Tehran, in a gesture of defiance first used in the 1979 Islamic revolution and now adopted by pro-reform protesters, again chanted Allahu Akbar (God is greatest) from their rooftops at nightfall on Monday.
Supporters of Mousavi, who says he seeks to purge the Islamic Republic of lies and deceit exposed during the elections, gathered in Tehran's Haft-e Tir square on Monday in defiance of a ban on demonstrations. Iran's state Press TV channel said they were dispersed.
Residents said riot police, some on motorbikes, and members of the religious Basij militia were out in force.
One witness said that from his balcony he had seen a group of protesters chanting slogans being attacked by the Basij, who dragged the demonstrators out of a house to which they had fled.
The Basiji were really aggressive and swearing at me to go inside, said the witness, who declined to be identified.
Iranian state television said on Tuesday Tehran had been calm for a second night. The presence of police and Basij forces in parts of the city has raised people's feeling of security, IRIB said.
Mousavi called on Sunday for new protests by his supporters in open defiance of senior religious leaders.
A U.N. statement issued by Secretary-General Ban Ki-moon's office said he urged the authorities to respect fundamental civil and political rights, especially the freedom of expression, freedom of assembly and freedom of information.
Ban urged the government and opposition to resolve their differences peacefully through dialogue and legal means.
Iranians on social networking sites called for mourning for Neda, a young woman shot dead on Saturday. Footage of her death has been watched by thousands on the Internet and her image has become an icon of the protests.
Witnesses said security officials prevented her funeral from going ahead, blocking roads leading to a central Tehran mosque where the ceremony was to have taken place.
Police were spraying paint on the cars of those who insisted on driving toward the mosque, said one witness.
Her fiance Caspian Makan told BBC Persian TV that Neda Agha-Soltan had been caught up accidentally in the protests.
She was near the area, a few streets away, from where the main protests were taking place, near the Amir Abad area. She was with her music teacher, sitting in a car and stuck in traffic, it quoted him as saying.
She was feeling very tired and very hot. She got out of the car for just a few minutes.