Iran's Foreign Minister Abbas Araghchi said there would not be any "hanging today or tomorrow," despite earlier threats from authorities to fast-track trials for protesters.
In an interview with US broadcaster Fox News, Mr Araghchi insisted that 10 days of peaceful demonstrations over Iran's economic hardships were followed by three days of violence orchestrated by Israel, and calm had been restored.
Earlier Amnesty International said Iranian authorities have committed mass unlawful killings "on an unprecedented scale" in their crackdown on protesters, citing verified video evidence and eyewitness reports.
"Security forces positioned on the streets and rooftops, including of residential buildings, mosques and police stations, have repeatedly fired rifles and shotguns loaded with metal pellets, targeting unarmed protesters frequently in their heads and torsos," the UK-based group said in a statement.
It denounced a "coordinated nationwide escalation" in the security forces' use of lethal force against protesters since 8 January when mass protests erupted and an internet shutdown came into force.
Meanwhile, US President Donald Trump said he had been told that killings in Iran's crackdown on nationwide protests were subsiding and that he believed there was currently no plan for large-scale executions, even as tensions between Tehran and Washington remained high.
Watch: Trump says he's been told the killings in Iran have stopped
The United States is withdrawing some personnel from bases in the Middle East, a US official has said, after a senior Iranian official said Tehran had warned neighbours it would hit American bases if Washington strikes.
With Iran's leadership trying to put down the worst domestic unrest the Islamic Republic has ever faced, Tehran is seeking to deter Mr Trump's repeated threats to intervene on behalf of anti-government protesters.
A US official, speaking on condition of anonymity, said the United States was withdrawing some personnel from key bases in the region as a precaution given heightened regional tensions.
Three diplomats said some personnel had already been advised to leave the main US air base in the region in Qatar, although there were no immediate signs of a large-scale evacuation of troops, as took place in the hours before an Iranian missile attack last year.
Mr Trump has repeatedly threatened to intervene in support of protesters in Iran, where thousands of people have been reported killed in a crackdown on the protests against clerical rule.
Iran and its western foes have both described the unrest, which began two weeks ago as demonstrations against dire economic conditions and rapidly escalated in recent days, as the most violent since the 1979 Islamic Revolution that installed Iran's system of clerical rule.
Over 3,400 killed during protests - IHR
Iranian security forces have killed at least 3,428 protesters in a crackdown on demonstrations, the Norway-based Iran Human Rights (IHR) NGO has said, adding that more than 10,000 people had also been arrested.
IHR said the jump in its verified toll was due to new information it received from within the Iranian health and education ministries, with at least 3,379 of the killings coming during the height of the protest movement from January 8 to 12.
The group's director Mahmood Amiry-Moghaddam condemned the "mass killing of protesters on the streets in recent days", while IHR warned that even the new figure represented an "absolute minimum" for the actual toll.
Meanwhile, an Iranian official said more than 2,000 people have died.
'The most violent repression'
Iran "had never faced this volume of destruction", Armed Forces Chief of Staff Abdolrahim Mousavi said, blaming foreign enemies. French Foreign Minister Jean-Noel Barrot described "the most violent repression in Iran's contemporary history".
According to an Israeli assessment, Mr Trump has decided to intervene, although the scope and timing of this action remain unclear, an Israeli official said.
The three diplomats told Reuters that some personnel had been advised to leave the US military's Al Udeid Air Base in Qatar by this evening.
One of the diplomats described the move as a "posture change" rather than an "ordered evacuation".
There was no sign of troops being moved off the base to a nearby soccer stadium and shopping mall, as took place last June in the hours before Iran targeted the base with missiles in retaliation for US airstrikes.
The US embassy in Doha had no immediate comment and Qatar's foreign ministry did not immediately respond to a request for comment.
Iranian authorities have accused the United States and Israel of fomenting the unrest, carried out by people it calls terrorists.
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Mr Trump has openly threatened to intervene in Iran for days, without giving specifics.
In an interview with CBS News yesterday, Mr Trump vowed "very strong action" if Iran executes protesters. He also urged Iranians to keep protesting and take over institutions, declaring "help is on the way".
The senior Iranian official, speaking on condition of anonymity, said Tehran had asked US allies in the region to prevent Washington from attacking Iran.
"Tehran has told regional countries, from Saudi Arabia and UAE to Turkey, that US bases in those countries will be attacked" if the US targets Iran, the official said.
Direct contacts between Iranian Foreign Minister Abbas Araqchi and US Special Envoy Steve Witkoff had been suspended, the official added.
The United States has forces across the region including the forward headquarters of its Central Command at Al Udeid in Qatar and the headquarters of the US Navy's Fifth Fleet in Bahrain.
The flow of information from inside Iran has been hampered by an internet blackout.
US-based HRANA rights group said it had so far verified the deaths of 2,403 protesters and 147 government-affiliated individuals, dwarfing tolls from previous waves of protests crushed by the authorities in 2022 and 2009.
The government's prestige was severely damaged by a 12-day Israeli bombing campaign in June - joined by the US – that followed setbacks for Iran's regional allies in Lebanon and Syria.
European countries triggered the restoration of UN sanctions over Iran's nuclear programme, worsening an economic crisis.
The unrest on such a scale had caught the authorities off guard at a vulnerable time, but it did not appear that the government faced imminent collapse, and its security apparatus was still in control, one Western official said.
The authorities have sought to project images showing they retain public support. Iranian state TV broadcast footage of large funeral processions for people killed in the unrest in Tehran, Isfahan and Bushehr, and other cities.
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Iran capable of launching counterattacks, says former CIA director
Meanwhile, a former director of the CIA has said US President Donald Trump must recognise that Iran has the capabilities to launch counterattacks in the event of US strikes.
Speaking on RTÉ's Drivetime, John Brennan said: "I’m sure the US Military is looking at all the different options in terms of what type of surgical strikes could be directed against the revolutionary guards but also trying to take out some of those capabilities Iran has to retaliate against US sites."
He said Iran has missile capabilities along the Gulf Coast and has anti-ship capabilities with missiles that could strike US naval vessels, as well as a terrorist capabilites as well.
If the US would strike, he said they would probably go after their Iranian Guard headquarters and facilities as well as some of the military capabilities along the Gulf that "pose a threat to US and international shipping".
Mr Brennan, who headed the agency between 2013 and 2017, said there are a lot of unknowns as to what is going to unfold in Iran in terms of the ongoing violence and whether or not the regime is going to fracture at some point.
"If the Iranian regime were to be toppled, I think there is going to be a protracted period of violence, confusion and chaos in the country.
"I think this is one of the things that the United States has to take into account, that just carrying out military strikes, that could lead to the toppling of the regime and does raise the prospect of a much more violent aftermath that could lead to even greater bloodshed," he said.
