More than 180 Iranian MPs appear to have snubbed an invitation to celebrate President Mahmoud Ahmadinejad's election win, local press reports say.
All 290 MPs were invited to the victory party on Wednesday night, but only 105 turned up, the reports say.
A BBC correspondent says the move is a sign of the deep split at the top of Iran after disputed presidential polls.
Meanwhile, Mr Ahmadinejad has told the US not to interfere in Iranian politics, the Fars news agency reports.
"I hope you [US President Barack Obama] will avoid interfering in Iran's affairs and express regret in a way that the Iranian people are informed of it," he was quoted as saying.
President Obama on Tuesday said he strongly condemned the "unjust" violence used on protesters.
There are signs the government is beginning to regain control. Wednesday appears to have had the least protests of any day since the result was announced.
But any idea that the opposition is about to go gently is probably an illusion.
This is an argument within Iran about the future of the country. The two sides have deeply differing views on how Iran should be run, and its place in the world. And neither is about to give ground.
Separately, key protest leader Mir Hossein Mousavi said on his website that he was facing "recent pressures" to withdraw his election challenge. "Access to people is completely restricted", the Associated Press news agency quoted him as saying.
Earlier, his website said 70 university professors were arrested immediately after meeting Mr Mousavi on Wednesday, and it was not clear where they had been taken.
Hundreds of opposition protesters and activists are believed to have been taken into custody and at least 17 people have died in the unrest that followed the 12 June election.
Severe reporting restrictions imposed on foreign media in Iran mean the BBC cannot verify the reports.
The Washington Times on Thursday said one of its freelance reporters, Iason Athanasiadis, a Greek citizen, was arrested at the airport as he tried to leave the country at the end of last week.
About 50 MPs in the Iranian parliament are reformist and would not have been expected to attend Mr Ahmadinejad's party.
One of those who reportedly did not attend is Parliament Speaker Ali Larijani, a high-profile figure who shares some of Mr Ahmadinejad's hardline views but has been critical of some aspects of the government's handling of the protests.
The high number of other MPs who stayed away is another indication that the disputed election has split the nation, says the BBC's Jeremy Bowen in Tehran.
An earlier BBC report wrongly said that 105 MPs did not turn up. It should have said that only 105 attended.
The opposition has vowed to continue with its legal challenges over the election result, which saw Mr Ahamadinejad declared an easy winner.
Mr Mousavi, his nearest rival, alleges the election was rigged and wants a re-run.
But time and options are running out for the opposition, says our correspondent.
The Guardian Council, which supervises elections, is expected to follow the line laid down by Supreme Leader Ayatollah Khamenei and say the result will stand, our correspondent adds.
Ayatollah Khamenei said again on Wednesday he would "not yield" over the election result.
Hours later, riot police were reported to have clashed again with demonstrators who defied government decrees to stop the street protests.
Witnesses said they saw police beat protesters with batons, fire tear gas and shoot into the air to disperse the crowds in central Tehran.
But Wednesday's protest was smaller than on previous days amid an increasingly heavy security presence on the streets.
Reformist election candidate Mehdi Karoubi on Thursday called off a planned ceremony to mourn those killed in the protests, saying he had been unable to get permission for it.
Iran has accused foreign governments of inflaming the protests.
President Ahmadinejad said US President Obama "made a mistake" with his comments about the crackdown in Iran.
"Our question is why he fell into this trap and said things that previously [former US President George W] Bush used to say," he was quoted by the semi-official Fars news agency as saying.
On Wednesday, Washington said it had rescinded invitations to Iranian diplomats to attend US 4 July celebrations held by embassies around the world.
A White House spokesman said Iranians had not replied anyway, but it was described by the BBC's Kim Ghattas in Washington as the first concrete step taken by the Obama administration in protest at the crackdown in Iran.
Also on Wednesday, Tehran said it was considering downgrading ties with Britain, after expelling two diplomats the previous day for "activities incompatible with their status".
The UK later announced that two Iranian diplomats were being sent home in retaliation.