Several people have been detained in Iran over the accidental shooting down of a Ukrainian passenger plane with a missile, the country's judiciary says.
Spokesman Gholamhossein Esmaili said investigations into the incident were continuing, but provided no details.
President Hassan Rouhani said the probe would be overseen by a "special court".
Ukrainian International Airlines flight PS752 was brought down shortly it took off from Tehran on Wednesday, killing all 176 people on board.
Most of the victims were Iranian and Canadian citizens.
For the first three days after the crash, Iran denied that its armed forces had shot down the Boeing 737-800 and suggested there had been a technical failure.
But as evidence mounted, the Revolutionary Guards said the operator of a missile defence system had mistaken the aircraft for a US cruise missile and fired at it.
Iran's air defences had been on high alert because the country had just fired ballistic missiles at two US bases in Iraq, in retaliation for the killing of top Iranian general Qasem Soleimani in a US drone strike in Baghdad.
The admission of responsibility provoked widespread anger in Iran, and protesters took to the streets in the capital and several other cities to denounce government lies and the clerical leadership including Supreme Leader Ayatollah Ali Khamenei.
What do we know about Iran's investigation?
Mr Esmaili told a news conference in Tehran that the judiciary would "investigate the causes and direct impact of the incident".
He added: "We will investigate the extent to which US warmongering caused this event. Several people have been detained and the investigation continues."
In a televised speech, President Rouhani said the judiciary would assemble a special court with a high-ranking judge and tens of experts to oversee the probe.
"This will not be a regular and usual case. The whole world will be watching this court," he added.
Mr Rouhani also stressed that Wednesday's "tragic event" should not be blamed on one individual.
"It's not only the person who pulled the trigger, but also others who are responsible," he said.
"Iranian armed forces admitting their mistake is a good first step," he added. "We should assure people that it will not happen again."
The president also said he wanted relevant officials to explain publicly why it took days for the authorities to disclose that missiles were fired at flight PS752.
The Iranian government's spokesman has denied that it was involved a cover-up, saying Mr Rouhani was not told what had happened until Friday evening.
The commander of the Revolutionary Guards' Aerospace Force said on Saturday that he had informed "officials" about the strike hours after the incident.
Mr Esmaili also said about 30 people had been arrested for "taking part in illegal gatherings" - an apparent reference to the recent anti-government protests.
"We have tolerance towards legal rallies," he added.
On Monday, Tehran's police force denied it had fired live ammunition at protesters, after at least one person was reportedly shot and wounded the previous night.
What are other countries saying?
UK Prime Minister Boris Johnson told the BBC on Tuesday that he was "glad" Iran had acknowledged making a "terrible mistake" in shooting down the plane.
"It's good that they've apologised. The most important thing now is that tensions in the region calm down," he added.
"I was in Oman just at the weekend, talking to people in the region, and they don't want a military conflict between the West and Iran."
Mr Johnson said the next step for Iran was to "repatriate in a dignified way" the bodies of the passengers and crew of flight PS752, who included three Britons.
Ukraine's Foreign Minister Vadym Prystaiko said on Monday that five of the countries that had citizens on board the airliner - Canada, Ukraine, Afghanistan, Sweden and an unnamed country - would meet in London on Thursday to discuss possible legal action.
He said the "grieving nations" would work out what steps to take individually and collectively to "bring the perpetrators to justice and how we can repay those families who have suffered".
Canada, which lost 57 citizens, will meanwhile play a more active role than international rules require in the investigation into the shooting down of the airliner, according to the head of its Transportation Safety Board (TSB).
The Canadian Transportation Safety Board's Kathy Fox said there were signs that Iran would allow the TSB to participate in the downloading and analysis of data from the plane's flight data recorder and cockpit voice recorder.