DUBAI (Reuters) - Protests erupted across Iran for a second day on Sunday, increasing pressure on the Islamic Republic’s leadership after it admitted its military shot down a Ukrainian airliner by accident, despite days of denials that Iranian forces were to blame.

“They are lying that our enemy is America, our enemy is right here,” one group of protesters chanted outside a university in Tehran, according to video posted on Twitter.

Other posts showed demonstrators outside a second university and a group of protesters marching to Tehran’s Azadi (Freedom) Square, as well as protests in other cities.

Some state-affiliated media carried reports of the university protests, which followed demonstrations on Saturday sparked by Iran’s admission that its military mistakenly shot down the plane on Wednesday, killing all 176 aboard, at a time when Tehran feared U.S. air strikes.

The Ukraine International Airlines plane was downed minutes after taking off from Tehran bound for Kiev on Wednesday. Many on board were Iranians with dual citizenship, while 57 were holders of Canadian passports.

Residents of the capital told Reuters that police were out in force on Sunday. Some protesters in Azadi Square first called on officers there to join them, then turned their anger on the authorities, chanting anti-government slogans including “Down with the dictator” - a reference to Supreme Leader Ayatollah Ali Khamenei, according to social media posts and Iranian media reports.

The semi-official ILNA news agency said police moved to disperse the protesters, who it said numbered as many as 3,000. Videos posted online showed demonstrators running from police who used batons and teargas.

Reuters could not authenticate the videos.

Public anger boiled up following days of denials by the military that it was to blame for the crash, issued even as Canada and the United States said it appeared that Iranian air defenses had shot down the airliner, probably in error.

“Apologise and resign,” Iran’s moderate Etemad daily wrote in a banner headline on Sunday, saying the “people’s demand” was that those responsible for mishandling the crisis quit.

The latest unrest adds to mounting pressure on the Iranian authorities, who are struggling to keep the crippled economy afloat under stringent U.S. sanctions.

Demonstrations against a hike in fuel prices turned political last year, sparking the bloodiest crackdown in the 40-year history of the Islamic Republic. About 1,500 people were killed during less than two weeks of unrest that started on Nov. 15, three Iranian Interior Ministry officials told Reuters, although international rights groups put the figure much lower and Iran called the report “fake news.”

After saying on Saturday that he was “inspired” by the courage of the demonstrators, U.S. President Donald Trump wrote on Twitter on Sunday: “To the leaders of Iran - DO NOT KILL YOUR PROTESTERS. Thousands have already been killed or imprisoned by you, and the World is watching. More importantly, the USA is watching. Turn your internet back on and let reporters roam free!”

Later on Sunday, Trump said on Twitter he did not care if Iran agrees to negotiate with the United States, after a senior adviser suggested the Islamic Republic would have no choice but to agree to talks.

‘IRAN’S ENEMIES WANT REVENGE’

About 2,000 people packed a vigil for the air-crash victims in Toronto on Sunday, and a similar number attended a memorial in Edmonton, Alberta, where Canadian Prime Minister Justin Trudeau spoke. His voice breaking, Trudeau told the vigil he would “pursue justice and accountability” for the victims. “We will not rest until there are answers,” he said.

The Transportation Safety Board of Canada (TSB) said it had obtained visas for two of its investigators to travel to Iran.

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A second team of investigators who specialize in aircraft recorder download and analysis will be deployed once TSB confirms where and when that activity would take place, the agency said.

The downing of the plane came as Iranian forces were on high alert for U.S. reprisals following tit-for-tat strikes.

A U.S. drone strike in Iraq on Jan. 3 killed prominent Iranian commander Qassem Soleimani, responsible for building up Iran’s network of proxy armies in Iraq and beyond. Tehran responded with missile strikes on U.S. targets in Iraq.

No U.S. soldiers were killed in the retaliatory attacks. But in the tense hours that followed, the Boeing 737-800 was cleared to take off from Tehran airport and brought down by a missile fired by mistake.

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Iranian President Hassan Rouhani apologized for what he said was a “disastrous mistake”. But a top Revolutionary Guards commander added to public anger when he said he had told the authorities on the same day as the crash that an Iranian missile had brought down the plane.

The Guards’ top commander, Hossein Salami, said that “we are more upset than anyone over the incident,” state media reported. Another commander said Iran did not intend to conceal the cause.

But others said Iran’s enemies, a term usually used to refer to Washington and its allies, were exploiting the incident.

“Iran’s enemies want to take revenge on the Guards for a military mistake,” said Ali Shirazi, Khamenei’s representative to the Quds Force, the elite overseas Guards unit that Soleimani headed, state media reported.

Iranian officials sought to portray the plane disaster as a second blow to a nation mourning after Soleimani’s death.

His funeral prompted huge public gatherings, which the authorities described as a show of national unity. But the displays of emotion have been swiftly overshadowed and protesters on Saturday tore up pictures of the slain general.

The killing of Soleimani dramatically escalated tensions between Tehran and Washington, following months of hostilities since Trump withdrew from a nuclear pact between Iran and world powers in 2018 and then toughened up sanctions.

Britain protested after its ambassador in Iran was briefly detained on Saturday. Iranian media said he was inciting protests. The envoy said he attended a vigil for plane victims.

British Foreign Secretary Dominic Raab condemned the arrest and said Iran “can continue its march towards pariah status ... or take steps to de-escalate tensions” with diplomacy.