President Trump issued a stark warning Sunday to Iran as leaders in Tehran gear up to deal with protesters who took to the streets after the government admitted to accidentally shooting down a Ukrainian passenger jet.

“To the leaders of Iran - DO NOT KILL YOUR PROTESTERS,” Trump tweeted. “Thousands have already been killed or imprisoned by you, and the World is watching. More importantly, the USA is watching.”

He added: “Turn your internet back on and let reporters roam free! Stop the killing of your great Iranian people!”

Numerous anti-government protests erupted at universities across Iran on Saturday with students calling for the resignation of Supreme Leader Ayatollah Ali Khamenei.

The protests come as Iran-U.S. tensions remain high, with Trump accusing Iran of planning attacks on four U.S. embassies, necesitating the drone strike last weekend that killed Iranian general Qassem Soleimani.

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One protester at Amir Kabir University in Tehran held up a banner that read, “[Expletive] you & your mistake," the New York Post reported. The banner also showed the names and photos of 16 students who died in the crash.

Crowds of students chanted for Iran's Revolutionary Guards to “let go of the country!” and also mentioned the deceased Soleimani, saying that he “was a murderer" and "his leader is too!”

The plane crash early Wednesday killed all 176 people on board, mostly Iranians and Iranian-Canadians. After initially pointing to a technical failure and insisting the armed forces were not to blame, Iranian authorities on Saturday admitted to accidentally shooting it down in the face of mounting evidence and accusations by Western leaders.

Iran downed the Ukrainian flight as it braced for retaliation after firing ballistic missiles at two bases in Iraq housing U.S. forces. The ballistic missile attack, which caused no casualties, was a response to the killing of Soleimani.

TRUMP TWEETS SUPPORT OF IRANIAN ANTI-GOVERNMENT PROTESTERS AFTER UKRAINIAN PASSENGER PLANE SHOT DOWN

Security forces were deployed in large numbers across the capital on Sunday in hopes of quelling demonstrations. Riot police in black uniforms and helmets massed in Vali-e Asr Square and at Tehran University and other landmarks as calls circulated for protests to be held later in the day.

Revolutionary Guard members patrolled the city on motorbikes and plainclothes security men were also out in force. People looked down as they walked briskly past police, hoping not to draw attention to themselves.

Hundreds of students gathered at Tehran's Shahid Beheshti University on Sunday to mourn the victims and protest against authorities for concealing the cause of the crash, the semi-official ISNA news agency reported. They later dispersed peacefully.

While there have been no reports of deaths or violence against the protesters so far, the memory of brutal reprisals by Iranian officials last November to protests over gas price increases is still fresh in the minds of many. The government shut down internet access for days, making it difficult to gauge the scale of the protests and the subsequent crackdown, but Amnesty International later said more than 300 people were killed.

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Secretary of State Mike Pompeo also weighed in on the protests, tweeting Saturday that the Iranian people have every right to be frustrated and deserve a brighter future.

"The voice of the Iranian people is clear. They are fed up with the regime’s lies, corruption, ineptitude and brutality of the IRGC under [Khamenei's] kleptocracy," he said.

Trump's voice of support for Iranian demonstrators marks a change from the lack of a public stance the U.S. took during the so-called Green Revolution in 2009, when protesters in the Islamic republic unsuccessfully asked the Obama adminstration to weigh in on the unrest roiling the country. The administration chose at the time not to take sides publically, and the protest movement was eventually violently surpressed by leaders in Tehran.

Fox News Nick Givas and The Associated Press contributed to this report.