Iran announced Tuesday (January 14th) its first arrests over the accidental shooting down of a Ukrainian airliner last week, as protestors vented their anger over the catastrophic blunder for a fourth consecutive day.
Making matters worse for the sanctions-hit country, Britain, France and Germany triggered a dispute resolution mechanism under the already tattered 2015 nuclear deal, prompting Iran to warn them of unspecified "consequences".
The Ukraine International Airlines plane was brought down by a missile shortly after takeoff on Wednesday, killing all 176 passengers and crew on board.
Iran has come under mounting international pressure to ensure its investigation into the tragedy is full and transparent.
The authorities' handling of the air disaster has also angered some Iranians.
AFP correspondents said around 200 mainly masked students gathered at Tehran University on Tuesday and were locked in a tense standoff with youths from the Basij militia loyal to the establishment.
Videos posted online Monday purported to show hundreds of protestors taking to the streets for a third consecutive night, apparently shouting slogans against Iran.
Protestors chanted "Death to dictator" on Sunday, Fars news agency reported, a rare move for a country where media usually refer to demonstrators as "rioters" and refrain from publishing such slogans.
The protests have been much smaller than nationwide demonstrations against fuel price hikes that turned deadly in November.
But one commentator said the latest rallies showed there was a "real rift between the people and the authorities".
"I hope that (police restraint) will continue and that no lives are lost, because this could be a catalyst for more protests," Mehdi Rahmanian, director of reformist daily Shargh, told AFP.
In another sign of growing dissent, a group of artists cancelled their participation in the Fajr festival, held each year on the anniversary of the 1979 Islamic Revolution, according to Hamshahri newspaper, which is owned by Tehran City Hall.
Tehran for days denied Western claims based on US intelligence that the Boeing 737 had been downed by a missile.
It came clean on Saturday when Iran's Islamic Revolutionary Guard Corps (IRGC) aerospace commander Brig. Gen. Amirali Hajizadeh acknowledged a missile operator had mistaken the plane for a cruise missile and opened fire independently.
At a televised news conference, the judiciary announced the first arrests had been made over the calamitous blunder, without specifying how many.
"Extensive investigations have been carried out and some people have been arrested," said spokesman Gholamhossein Esmaili.
Esmaili also said around 30 people had been arrested in the protests over the air disaster.
'World will be watching'
The announcement came shortly after President Hassan Rouhani said everyone responsible for the disaster must be punished.
"For our people it is very important in this incident that anyone who was at fault or negligent at any level" face justice, Rouhani said.
"Anyone who should be punished must be punished.
"The judiciary must form a special court with a high-ranking judge and dozens of experts... The whole world will be watching," Rouhani said.
The Kiev-bound plane was shot down at a time when Iran's armed forces were on heightened alert after launching a volley of missiles at Iraqi bases housing US troops.
Iran fired the missiles in retaliation for a US drone strike on January 3rd that killed Qassem Soleimani, the head of the IRGC's Quds Force foreign operations arm.
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 (TSB) said its investigators flying to Tehran would be granted access to the wreckage and black box flight recorders of the downed airliner.
"There have been early signs that Iran is allowing the TSB to play a more active role than is normally permitted," its chair Kathy Fox said.