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 after taking off from Tehran on Wednesday, killing all 176 people on board.
Most were Iranian and Canadian citizens.
For the first three days after the crash, Iran denied that its armed forces had shot down the plane 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.
President Rouhani stressed that the “tragic event” should not be blamed only on the individual who “pulled the trigger”.
“Iranian armed forces admitting their mistake is a good first step,” he added. “We should assure people that it will not happen again.”
Iran’s air defences had been on the highest state of alert before the shooting because the country had just fired more than a dozen ballistic missiles at US bases in Iraq in retaliation for the killing of 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 its clerical rulers, including Supreme Leader Ayatollah Ali Khamenei.
UK Prime Minister Boris Johnson said 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”.