Iran’s supreme leader Ayatollah Ali Khamenei on Saturday accused US President Donald Trump of being responsible for “casualties” during a protest wave in the country that rights groups said was met with a deadly crackdown.

“We hold the American president guilty for the casualties, damages and accusations he has levelled against the Iranian nation,” he told a crowd of supporters during an address marking a religious holiday.

“This was an American conspiracy,” Khamenei said, adding that “America’s goal is to swallow Iran … the goal is to put Iran back under military, political and economic domination”.

“By God’s grace, the Iranian nation must break the back of the seditionists just as it broke the back of the sedition,” he said.

“We do not intend to lead the country to war, but we will not spare domestic criminals,” he added, saying that “international criminals” were “worse” and would also not be spared punishment.

Iranian authorities have blamed the United States for fuelling a “terrorist operation” that they say hijacked peaceful protests over the economy.

Iran was rocked by weeks of demonstrations sparked by anger over economic hardship that exploded into the biggest protests against the Islamic republic in more than three years.

Meanwhile, after repeated warnings, Trump on Thursday had changed his stance on military intervention in Iran, adopting a “watch it and see” posture instead.

He had cited assurances from “very important sources on the other side” indicating that Tehran had ceased using lethal force against demonstrators.

“They’ve said the killing has stopped and the executions won’t take place,” Trump said. Asked by a reporter if US military action was now off the table, the president replied: “We’re going to watch it and see what the process is.”