Hundreds of protesters have taken to the streets in Iran's capital, Tehran, to vent anger at officials, calling them liars for having denied shooting down a Ukrainian passenger plane.
Protests took place outside at least two universities, with tear gas reportedly fired.
US President Donald Trump tweeted support for the "inspiring" protests.
Iran on Saturday admitted downing the jet "unintentionally", three days after the crash that killed 176 people.
Ukraine International Airlines flight PS752, en route to Kyiv, was shot down on Wednesday near Imam Khomeini Airport in Tehran shortly after take-off, and only hours after Iran had fired missiles at two air bases housing US forces in Iraq.
Those attacks were Iran's response to the US killing of senior Iranian commander Qasem Soleimani in a drone strike in Baghdad on 3 January.
Dozens of Iranians and Canadians, as well as nationals from Ukraine, the UK, Afghanistan and Sweden died on the plane.
Students gathered outside at least two universities, Sharif and Amir Kabir, reports said, initially to pay respect to the victims. Protests turned angry in the evening.
The semi-official Fars news agency carried a rare report of the unrest, saying up to 1,000 people had chanted slogans against leaders and tore up pictures of Soleimani.