Hundreds of protesters chanting anti-government slogans gathered in central Tehran on Saturday evening after the government of Iran admitted that it had shot down a Ukrainian airliner on Wednesday killing all 176 passengers on board. Protesters demanded the resignation of senior officials and tore down posters of killed Quds Force leader Qassim Sulimani, whose death on January 3 in a US airstrike near Bagdhad airport, sparked the retaliation from Iran in which the airliner was shot down. Riot police took to the streets in an attempt to disperse the protesters Teleqani Street and Hafez Avenue between the Tehran Polytechnic University and the Tehran Campus of Kharazmi University. The demonstration, covered in a rare report by the semi-official Fars news agency that is seen as close to the country’s Revolutionary Guard, comes weeks after Iran killed hundreds of anti-government protests in a crackdown on dissent. Iran admitted on Saturday that its military “unintentionally” shot down the Ukrainian jetliner that crashed earlier this week, killing all 176 aboard, after the government had repeatedly denied western accusations that it was responsible. The plane was shot down early on Wednesday, hours after Iran launched a ballistic missile attack on two military bases housing US troops in Iraq in retaliation for the killing of Suleimani. On board were 82 Iranians, 63 Canadians, 11 Ukrainians, 10 Swedes, four Afghans, three Germans and three British nationals, according to a tweet from Ukrainian Foreign Minister Vadym Prystaiko. “In such a condition, because of human error and in an unintentional way, the flight was hit,” the Iranian Islamic Revolutionary Guard said in a statement. It apologised for the disaster and said it would upgrade its systems to prevent such “mistakes” in the future. He said that the military received information of incoming cruise missiles in response to their targeting of US bases in Iraq and so air defences were on high alert. "Given the information provided to the operator that it was a war situation and cruise missiles had been fired, this person identified this as a [missile]," Brig Gen Amirali Hajizadeh, the aerospace commander of the Revolutionary Guards, said on Saturday. "He was obliged to make contact and get verification. But apparently, his communications system had some disruptions. "Either the 'jamming' system was the cause or the network was busy or whatever, he couldn't get in touch," said the Iranian general. "He had 10 seconds to decide. "Unfortunately under these circumstances, he made this bad decision, the missile was fired and the plane was hit and then... it turned and the spot that it crashed at was here," he said, pointing to a map. Brig Gen Hajizadeh said on Saturday that the missile exploded next to the plane before it went down. "It was a short-range missile that exploded next to the plane. That's why the plane was able" to continue flying for a while, Brig Gen Hajizadeh said in remarks aired on state TV. "It exploded when it hit the ground." Brig Gen Hajizadeh apologized to the families of those killed and said that, “When I realized that this had happened, I really wished I had died and I hadn't seen such an accident.” He denied that there had been an attempt to hide the truth and said the delay in admitting responsibility was due to internal investigations to confirm what had happened. Until Friday, Iranian officials had denied that the plane was brought down by a missile and accused western governments of “psychological warfare”. But the US and Canada, citing intelligence, said they believed Iran shot down the aircraft. Brig Gen Hajizadeh said that denials by civilian government officials and agencies were also not lies but were because the investigation into the shooting down of the plane was done by a classified team within the Revolutionary Guard and therefore not disclosed to the government before the weekend. President Hassan Rouhani tweeted that human error had caused “the horrific crash of the Ukrainian plane” and added that investigations were ongoing identify and prosecute those responsible. After a call with Iran's President, Ukraine’s President Volodymyr Zelensky said that acknowledging the plane was shot down was a step in the right direction. Mr Zelensky said that Iranian President Hassan Rouhani apologized on behalf of the country and admitted completely that the crash was caused by a mistake from the military. He added that he had been promised that those responsible would be held to account. In an address on Saturday evening, Prime Minister Justin Trudeau said: "We need closure." He said Canadian investigators were on the ground despite the country having no diplomatic ties with Tehran and that "Canada will not rest until we get the full accountability, justice and closure that the families deserve," he says. In answer to a question he said that while Iranian authorities may charge an individual or individuals responsible, there was also the recognition that there is “system-wide culpability” for the disaster. The EU Aviation Safety Agency (EASA) said on Saturday that European airlines should avoid Iranian airspace until further notice. The advice expands on an earlier EASA recommendation that national authorities bar airlines from overflying Iran below 25,000 feet. It was issued "in light of the statement from Iran that its armed forces accidentally shot down a Ukrainian passenger aircraft", EASA said. “This is the right step for the Iranian government to admit responsibility, and it gives people a step toward closure with this admission," said Payman Parseyan, a prominent Iranian-Canadian in western Canada who lost a number of friends in the crash. “I think the investigation would have disclosed it whether they admitted it or not," Mr Parseyan told the Associated Press. "This will give them an opportunity to save face.” Expressions of condolence over the incident from the supreme leader and President Hassan Rouhani failed to calm angry Iranians, who used social media to express their outrage against the establishment for concealing the truth. "It is a national tragedy. The way it was handled and it was announced by the authorities was even more tragic," said Ali Ansari, a moderate cleric, according to Iran's semi-official Ilna news agency. Many Iranians asked why authorities did not close down Tehran's airport and the country's airspace and others pointed out that the military had been careful not to kill US troops in their strikes on Iraqi airbases. "They were so careful not to kill any American in their revenge for Suleimani. But they did not close the airport? This shows how much this regime cares for Iranians," said Mira Sedaghati in Tehran by telephone. Others were angered at the delay in admitting the “mistake.” "Unintentionally? What does it mean? They concealed this huge tragic news for days just to mourn for Suleimani. Shame on you," said Reza Ghadyani, in Tabriz city. The country held three days of funeral processions for Suleimani, who was head of the Revolutionary Guards' overseas Quds Force and a national hero. Hundreds of thousands of people participated across the country. Some Iranians called for the resignation of officials, dismissing their apologies. "You took your revenge from Iranians," tweeted Ahmad Batebi on his @radiojibi Twitter account, in response to Rouhani's tweet saying that "The Islamic Republic of Iran deeply regrets this disastrous mistake". "Only resignation," tweeted Sadeq on his @sadeq1367 account In a Twitter message on Saturday, Foreign Minister Mohammad Javad Zarif cast some of the blame for the plane disaster on what he called US adventurism. "It's the end line Mr Minister! You ruined everything!," responded Bita Razaqi on @bitarazaqi. The disaster is the latest in accidental shootings of civilian aircraft. In 2003, a DHL cargo jet was struck by a surface-fired missile shortly after taking off from Baghdad during the US-led occupation of Iraq, forcing pilots to make an emergency landing. No one was hurt. In 1988, a US Navy missile cruiser, the <em>USS Vincennes</em>, downed an Iran Air Airbus A300 over the Arabian Gulf, killing 290 passengers and crew. The US military said it mistook the airliner for an Iranian fighter jet, an account disputed by Iran. In 2001, a Ukrainian air-defence station accidentally shot down a Siberian Airlines jet over the Black Sea, killing the 78 passengers and crew on board. Russian investigators concluded that the Ukrainian forces had fired two missiles at a drone as part of a military exercise, and one of them flew 240 kilometres past its target and detonated near the airliner, causing it to plunge into the sea, the <em>New York Times</em> reported at the time. The July 2014 episode involving the Malaysian Airlines plane has been one of the most well-documented cases. The Boeing 777 carrying 298 people was shot down by a Russian-made Buk surface-to-air missile fired from rebel-controlled territory in eastern Ukraine. The region is the site of a conflict between pro-Russia separatists and Ukrainian military forces and two military aircraft had been downed just days earlier, an international team concluded.