'Death to Trump's America': Iranians celebrate 1979 revolution
In a Tehran rally attended by hundreds of thousands of people in the capital, President Hassan Rouhani addressed the crowds, warning against those using "threatening language" with Iran.
"This turnout is a response to false remarks by the new rulers in the White House and the people are telling the world through their presence that the Iranian people must be spoken to with respect," Rouhani said.
"Iranians will make those using threatening language against this nation regret it," he said.
"Anyone threating Iran's government and armed forces should know that our nation is vigilant."
US flags were burnt in the rallies while some people carried pictures of Trump, Israeli Prime Minister Binyamin Netanyahu as well as British Prime Minister Theresa May, captioned "Death to the Devil Triangle", according to Reuters.
Some people threw balls and darts targeting pictures of Trump and Netanyahu, while pictures of current and former US presidents were flattened on the road and trampled by some participants.
Many ranking officials attended the ceremony Tehran, including Qassem Soleimani, a general who heads the Iranian Revolutionary Guard's elite Quds Force that focuses on foreign operations like the war in Syria.
State television aired footage of commemorations in Tehran and other cities and towns across the country, many of them in sub-zero weather.
The rallies commemorate February 11, 1979, when followers of Ayatollah Ruhollah Khomeini ousted the US-backed Shah Reza Pahlavi.
Agencies contributed to this report.