Iran's leaders are facing a second day of protests following their admission the military shot down a Ukrainian passenger plane, killing all 176 people on board, many of them Iranians.
Demonstrators gathered at universities in Tehran and at sites in other cities, calling for senior officials to go.
Riot police have been sent to Tehran's Azadi Square and at other landmarks.
Iran admitted "unintentionally" hitting the plane after initially denying it amid rising tensions with the US.
The plane, en route to the Ukrainian capital, Kyiv, was shot down near Tehran last Wednesday, shortly after Iran had launched missiles at two airbases housing US forces in Iraq.
Those strikes were a response to the US killing of senior Iranian commander Qasem Soleimani in a drone strike in Baghdad on 3 January.
What has happened at Sunday's protests?
Demonstrators attended new protests despite a large deployment of security forces.
Riot police, members of the elite Revolutionary Guard on motorbikes, and plainclothes security officials were out in force.
In one apparently symbolic act rejecting state propaganda, video showed students taking care not to walk over US and Israeli flags painted on the ground at Shahid Beheshti university in Tehran.
In some social media clips, protesters can be heard chanting anti-government slogans, including: "They are lying that our enemy is America, our enemy is right here."
Unverified social media footage showed clapping and chanting protesters in Tehran's Azadi square - and reports of clashes with security forces.
Scores of protesters were also reported at sites in other cities.
Those who decide to continue demonstrating will be mindful of the violence with which the security forces have dealt with protest movements in the past. the BBC's Arab affairs editor Sebastian Usher says.