Iran's leaders are facing a second day of protests after admitting 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 other landmarks.
Dozens of Iranians and Canadians, as well as nationals from Ukraine, the UK, Afghanistan and Sweden died on the plane.
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.
US President Donald Trump had ordered the strike, saying Soleimani was preparing attacks against four US embassies, but his Defence Secretary Mark Esper told CBS's Face the Nation on Sunday that he "didn't see" that specific evidence - even though he shared the president's belief that there "probably and could've been attacks on additional embassies".
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 could 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, BBC Arab affairs editor Sebastian Usher said.
On Saturday, students had gathered outside two universities. They initially did so to pay respect to the victims, but angry protests erupted later in the evening and tear gas was reportedly fired to disperse them.
A number of Iranian newspapers have covered the vigils for the plane victims alongside headlines such as "shame" and "unforgivable".
There has also been praise for what one pro-government newspaper called Iran's "honest" admission of error.
There were also protests on Sunday in Tehran in support of Soleimani, and opposing the US and UK.
What has the international reaction been?
Trump on Sunday repeated warnings that Iran should not target anti-government protesters, saying, "the World is watching. More importantly, the USA is watching".
Britain, meanwhile, has condemned the arrest of the UK ambassador to Iran in Tehran as a "flagrant violation of international law".
Foreign Secretary Dominic Raab said Rob Macaire was detained after attending a vigil where he was paying respects to victims of the crash, some of whom were British.
Macaire said he left the vigil when some people started chanting and had played no part in the demonstration.
Iran on Sunday summoned the ambassador to complain about "his unconventional behaviour of attending an illegal rally", the foreign ministry website said.
Iranian protesters set a UK flag alight in front of the UK embassy on Sunday.
How did the Iranian admission unfold?
For three days, Iran denied reports its missiles had brought down the plane, with one spokesman accusing Western nations of "lying and engaging in psychological warfare".
On Saturday morning, a statement read on state TV accepted the plane had been shot down.
Brig-Gen Amir Ali Hajizadeh, the Revolutionary Guards' aerospace commander, said a missile operator had acted independently and alone, mistaking the plane for a "cruise missile".
He also said he had informed the authorities about what had happened on Wednesday, raising questions about why Iran had denied involvement for so long.
Both Ukrainian President Volodomyr Zelensky and Canadian Prime Minister Justin Trudeau have demanded accountability from Iran.
Trudeau said on Saturday there must be a full investigation with "full clarity on how such a horrific tragedy could have occurred".