Protests have erupted across Iran for a second day, piling pressure on the leadership after the military admitted it mistakenly shot down a Ukrainian airliner.
"They are lying that our enemy is America, our enemy is right here," a group of protesters outside a university in Tehran chanted, according to video clips posted on Twitter.
Scores of demonstrators were shown outside another university in the capital and at gatherings in other cities on Sunday.
Some state-affiliated media also carried reports of university protests, following Saturday's demonstrations sparked by Iran's announcement its military mistakenly brought down the Ukrainian plane on Wednesday, killing all 176 onboard.
The public anger followed days of denials by the military, issued even as Canada and the US said a missile was responsible.
Riot police fired tear gas at thousands of protesters in the capital on Saturday, where many had chanted "death to the dictator", directing their anger at the Iran's Supreme Leader Ayatollah Ali Khamenei.
"Apologise and resign," Iran's moderate Etemad daily wrote in a banner headline on Sunday, saying the "people's demand" was for those responsible for mishandling the plane crisis to quit.
US President Donald Trump warned Iranian authorities not to harm demonstrators.
Protesters chant slogans during a demonstration in Tehran, Iran, 12 January, 2020 Source: AAP
"To the leaders of Iran - DO NOT KILL YOUR PROTESTERS. Thousands have already been killed or imprisoned by you, and the World is watching," he posted on Twitter.
The Ukraine International Airlines plane was shot down minutes after taking off from Tehran on Wednesday, when Iranian forces were on alert for US reprisals following tit-for-tat strikes.
Many on board were Iranians with dual citizenship, while 57 held Canadian passports.
Iran's president said it was a "disastrous mistake" and apologised.
But a top Revolutionary Guards commander added to public fury when he said he told the authorities on the same day as the crash that an Iranian missile had struck the plane.
Britain said its ambassador in Iran was briefly detained on Saturday, which Iranian media said was because he was inciting protests.
The envoy said he attended a vigil for plane victims.
Iran's authorities summoned him on Sunday, while members of the hardline Basij militia gathered outside the mission holding signs demanding the "treacherous embassy" be closed, state-affiliated media reported.
British Prime Minister Boris Johnson and German Chancellor Angela Merkel spoke with each other on Sunday and condemned the arrest.
"On Iran, they discussed the tragic loss of life on the Ukraine International Airlines passenger jet. They condemned Iran's arrest of the UK Ambassador to Tehran as a violation of international law," Johnson's spokesman said in a statement.
Protests inside Iran followed a build-up of tension between Iran and the US, which withdrew from Tehran's nuclear pact with world powers in 2018 and then toughened up sanctions.
On January 3, a US drone strike in Iraq killed prominent Iranian commander Qassem Soleimani, responsible for building up Iran's network of regional proxy armies in Iraq and beyond.
Tehran responded with missile strikes on US targets in Iraq.
