Iran's judiciary announced the arrests of an unspecified number of suspects after the accidental shoot-down of a commercial passenger jet during a major confrontation with the United States last week.

In comments carried by state media, spokesman Gholamhossein Esmaili said on Tuesday "extensive investigations have taken place and some individuals are arrested". He did not offer additional details.

Al Jazeera's Dorsa Jabbari, reporting from the capital Tehran, said one person detained was the individual who posted video of the missile striking the airliner.

"We just received a statement from the Revolutionary Guard saying the person who filmed the moment of the strike that took place - the video that was shared around the world that brought in question the narrative the Iranians said initially - that person has now been detained," she said.

"He's been held for questioning about the events he witnessed and the footage he filmed."

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Last Wednesday's downing of the Ukrainian airliner, en route to Kyiv from Tehran, killed all 176 passengers and crew on board. It happened just hours after Iran launched missile attacks on US targets in Iraq in retaliation for the US assassination of top Iranian commander Qassem Soleimani in Baghdad on January 3.

After days of denials, Iran on Saturday admitted its Islamic Revolutionary Guard Corps (IRGC) shot down the plane in a "disastrous mistake", saying air defences were fired in error while on alert after the attacks against two Iraqi bases hosting US troops.

US President Donald Trump previously threatened to strike 52 targets within Iran if Tehran targeted US citizens or assets following Soleimani's killing.

Iran's delayed acknowledgement of the shootdown triggered small protests in Tehran and elsewhere, with hundreds of people taking to the streets to direct their ire towards senior officials, including Supreme Leader Ali Hosseini Khamenei, amid allegations of being misled.

Videos posted on social media that could not be independently verified appeared to show security forces firing live ammunition and tear gas to disperse protesters. The government has denied a cover-up and police rejected reports it opened fire on demonstrators.

Rouhani calls for special court

In a televised address on Tuesday, Iran's President Hassan Rouhani promised a thorough investigation into the "unforgivable error" of shooting down the plane, the latest in a series of apologies from a leadership grappling with public anger.

Rouhani called for a special court to be set up with a ranking judge and dozens of experts to investigate the "tragic event".

"This is not an ordinary case. The entire world will be watching this court," Rouhani said, adding everyone responsible in the accident must be punished.

"For our people, it is very important in this incident that whoever was at fault or negligent at any level" faces justice, Rouhani said. "Anyone who should be punished must be punished."

The president called the government's admission that Iranian forces shot down the plane the "first good step".

"We should assure people that it will not happen again," Rouhani said, adding that his government was "accountable to Iranian and other nations who lost lives in the plane crash".

Al Jazeera's Assed Baig, reporting from Tehran, said Rouhani's comments were "a watershed moment in this country because people aren't used to the military and state institutions taking state responsibility and accepting that they are wrong".

Baig added Rouhani mentioned the downing of the plane was not the fault of just one person operating the air defence system - rather, there were many issues involved.

"He also said that ultimately it's the US that's responsible for the heightened level of tension, again referring to Trump's threat to target 52 sites but added this isn't an excuse for the military and other people," Baig said.

International experts

Most of those on board the flight were Iranians or dual nationals. Canada, Ukraine, Britain and other nations who had citizens on the plane have scheduled a meeting on Thursday in London to consider legal action against Tehran.

Iran has invited experts from Canada, France, Ukraine and the US to take part in the probe into the air disaster.

On Monday night, Canada's Transportation Safety Board said its investigators flying to Tehran would be granted access to the wreckage and black box flight recorders of the downed airliner.

"The government from the very beginning invited international teams for the investigation. If there was going to be a cover-up they wouldn't have done that," said Mohammad Marandi, head of American studies at the University of Tehran.

"The government and the armed forces protected the black box. They could have damaged it beyond recognition and say that it was destroyed in the crash; they didn't do so. They protected it."