Iranian authorities said they would teach an exemplary lesson to "rioters" held in the worst unrest since the birth of the Islamic Republic and accused Western powers of inciting the violence.
Riot police and Basij militia on Tehran's main squares warded off the mass protests that have marked the week since disputed elections. Iran's hardline leadership appeared to have gained the ascendancy, at least for the moment.
The conflict, which has yielded unprecedented signs of division in the religious leadership, began to play out on the diplomatic level with Britain the focus of anger. London said two of its diplomats had been expelled from Iran and it had ordered out two Iranians in retaliation.
A group of about a hundred hardliners gathered in front of the British embassy in Tehran, chanting "British embassy should be closed", a witness said.
Supporters of hardline anti-Western President Mahmoud Ahmadinejad held a news conference in the building of the old US embassy that was seized by students after the Islamic Revolution in 1979 and held with 52 US hostages for 444 days.
"We don't need to have such useless relations with Britain ... If Britain continues its interference in Iran, we will destroy their houses over their heads," said one of the student leaders.
Iran's top legislative body, the Guardian Council, rejected demands for a rerun from former prime minister Mirhossein Mousavi, who says he is the rightful victor in elections that were rigged, and pro-reform cleric Mehdi Karoubi.
Mr Mousavi, himself a scion of the religious establishment, says he does not seek to undermine the Islamic Republic but to purge it of what he calls lies and deceit.
Iranian state television, in a broadcast clearly intended to discredit opponents defying a ban on protests, paraded people it said had been arrested during weekend violence.
"I think we were provoked by networks like the BBC and the VOA (Voice of America) to take such immoral actions," one young man said. His face was shown but his name not given.
A woman whose face was pixellated said she had carried a "war grenade" in her hand-bag. "I was influenced by VOA Persian and the BBC because they were saying that security forces were behind most of the clashes.
"I saw that it was us protesting ... who were making riots. We set on fire public property, we threw stones ... we attacked people's cars and we broke windows of people's houses."
At least 10 protesters were killed in the worst violence on Saturday, and about seven more early last week.
The troubles have erupted against a background of tension between the West and Iran, a major oil and gas producer and pivotal factor in regional stability.
Mr Mousavi was quoted by an ally on Saturday as calling for a national strike if he was arrested.
Mr Karoubi signalled today opposition would continue, calling on Iranians to hold ceremonies on Thursday to mourn those killed at protests.
The official IRNA news agency quoted senior judiciary official Ebrahim Raisi as saying on state television late yesterday: "Those arrested in recent events will be dealt with in a way that will teach them a lesson." 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," Mr Raisi said.
Reuters