Iranians staged protests for a third day on Monday over the military's shooting down of a Ukrainian plane and the government’s attempt to conceal its role although they were restricted to universities amid a heavy security presence and following reports of gunfire and tear gas being used against protesters the night before. An internet monitor reported a slowdown in connectivity near Tehran's Sharif University in a repeat of a tactic used during a crackdown on protests over fuel price increases in November. The latest protests broke on Saturday after the Revolutionary Guard admitted to shooting a Ukrainian passenger jet leaving Tehran by mistake, killing all 176 on board. Video of protests in Tehran’s Azadi Square on Sunday night showed demonstrators fleeing as a tear gas canister lands among them. People cough and sputter while trying to escape the fumes, with one woman calling out in Farsi: “They fired tear gas at people! Azadi Square! Death to the dictator!” Another video shows a woman being carried away leaving a trail of blood. Tehran’s police chief, General Hossein Rahimi, denied that his officers opened fire, although the semi-official Fars news agency reported that police had “shot tear gas in some areas”. Fars, which is close to the Revolutionary Guard, carried videos purportedly shot Sunday night showing demonstrators chanting: “We are children of war. Fight with us, we will fight back.” Another Fars video showed demonstrators in Tehran tearing down a poster of Qassem Suleimani, the Revolutionbary Guard commander killed in a US air strike in Baghdad. US President Donald Trump has openly encouraged the demonstrators and warned the government not to fire on them, while German Foreign Minister Heiko Maas tweeted that “we are following the protests in Tehran very attentively,” adding that Iranians “have a right to free expression without repression and persecution”. Most of the people aboard the Ukraine International Airlines jet were Iranians and Iranian-Canadians. For three days, Iranian officials ruled out any attack on the plane, suggesting the crash of Flight 752 was caused by a technical failure. Only on Saturday did authorities acknowledge shooting it down, as evidence mounted and after western leaders accused Iran of culpability. In addition to the street protests, Iran’s government has also faced harsh criticism from prominent artists, athletes and journalists. A number of artists, including famed director Masoud Kimiai, withdrew from an upcoming international film festival. Two state TV hosts resigned in protest over the false reporting about what happened to Flight 752. Taraneh Alidoosti, one of Iran’s most famous actresses, posted a picture of a black square on Instagram with the caption: “We are not citizens. We are hostages. Millions of hostages.” Saeed Maroof, the captain of Iran’s national volleyball team, also wrote on Instagram: “I wish I could be hopeful that this was the last scene of the show of deceit and lack of wisdom of these incompetents but I still know it is not.” He said that despite Iran’s national team qualifying for the 2020 Tokyo Olympics after years of effort, “there is no energy left in our sad and desperate souls to celebrate.” President Hassan Rouhani promised a "thorough investigation" into the disaster in a phone call with Sweden's Prime Minister Stefan Lofven, his office said. The majority of those on Flight PS752 were Iranians and Canadians, including dual nationals. Others were Ukrainians, Afghans, Britons, seven Swedes and 10 people who resided in the Scandinavian country. "We must strive to ensure that such a shocking incident is not repeated anywhere in the world," Mr Rouhani said. The president noted the disaster occurred at a time of heightened tensions in the region after the US killing of Suleimani in Baghdad on January 3. "We must all join hands to bring security back to the region and allow peace to prevail." Iran has come under mounting international pressure to ensure its investigation into the tragedy is full and transparent. Prime Minister Justin Trudeau told a memorial event in Edmonton for the 57 Canadians who lost their lives that "this tragedy struck our Iranian-Canadian community". "We want to assure all families and all Canadians that we will not rest until there are answers," he said. "We will not rest until there is justice and accountability." Iran has invited experts from Canada, France, Ukraine and the United States to take part in the probe. Despite footage from the site of disaster appearing to show bulldozers at work, the Revolutionary Guard's top commander denied evidence had been tampered with. "We didn't touch anything," said Major General Hossein Salami. "We didn't move the wreckage of the aircraft, we didn't change the scene, we didn't move the air defence system, and we didn't [alter] the radar readings." On the diplomatic front, Britain summoned Iran's ambassador to London after its Tehran envoy was briefly arrested for allegedly attending the demonstration.