NEW YORK: US President Donald Trump said Saturday the United States was monitoring Iranian demonstrations closely, warning against any new “massacre” as protests broke out after Tehran admitted to shooting down a passenger plane. Iran said earlier it unintentionally downed a Ukrainian jetliner outside Tehran, killing all 176 people aboard, in an abrupt about-turn after initially denying Western claims it was struck by a missile. The firing came shortly after Iran launched missiles at bases in Iraq housing American forces. President Hassan Rouhani said a military probe into the tragedy had found “missiles fired due to human error” brought down the Boeing 737, calling it an “unforgivable mistake.” At a student protest to pay tribute to the crash victims on Saturday, Iranian authorities briefly detained Britain’s ambassador, in what the British government called a violation of international law. He was later released. Donal Trump told Iranians in tweets in both English and Farsi that he stands by them and is monitoring the demonstrations. “To the brave, long-suffering people of Iran: I’ve stood with you since the beginning of my Presidency, and my Administration will continue to stand with you,” he tweeted. “There can not be another massacre of peaceful protesters, nor an internet shutdown. The world is watching,” he added, apparently referring to an Iranian crackdown on street protests that broke out in November. “We are following your protests closely, and are inspired by your courage,” he said. The new demonstrations follow an Iranian crackdown on street protests that broke out in November. Amnesty International has said it left more than 300 people dead. Internet access was reportedly cut off in multiple Iranian provinces ahead of memorials planned a month after the protests. Canadian Prime Minister Justin Trudeau has demanded that Iran provide “full clarity” on the downing of the plane. Ottawa says the dead included 57 Canadians. Iran’s Supreme Leader Ayatollah Ali Khamenei also offered his condolences and ordered the armed forces to address “shortcomings” so that such a disaster does not happen again. Tehran’s acknowledgement came after officials in Iran denied for days Western claims that the Ukraine International Airlines plane had been struck by a missile in a catastrophic error. The Kiev-bound jet slammed into a field shortly after taking off from Tehran’s Imam Khomeini International Airport on Wednesday. The crash came hours after Tehran launched missiles at bases hosting American forces in Iraq in response to the killing of top Iranian general Qasem Soleimani in a US drone strike. Fears grew of an all-out war between Iran and its arch-enemy the United States, but those concerns have subsided after Trump said Tehran appeared to be standing down after targeting the US bases.