Russia has warned the United States not to interfere in what Moscow calls Iran’s “domestic affairs”.

Donald Trump has pledged “great support” for Iranian protesters, who have been staging rallies across Iran over the past week against the country’s clerical leadership.

“Such respect for the people of Iran as they try to take back their corrupt government,” the US President tweeted. “You will see great support from the United States at the appropriate time!”

“We warn the US against attempts to interfere in the internal affairs of the Islamic Republic of Iran,” Sergei Ryabkov, the Russian deputy foreign minister said in an interview with state news agency TASS.

Mr Ryabkov also said Washington “is tempted to use the moment to raise new issues with regard to the JCPOA”, the Joint Comprehensive Plan of Action that limits Iran’s nuclear programme, including restrictions on uranium enrichment for 10 years.

At least 21 people have been killed in the demonstrations, which are the largest to strike Iran since its disputed 2009 presidential election.

It is not immediately clear if the drop in reports of new demonstrations means the protests are subsiding or whether the authorities’ blocking of social media apps has stopped protesters from offering new images of rallies.

Iran protests – in pictures Show all 11 1 /11 Iran protests – in pictures Iran protests – in pictures University students at an anti-government protest inside Tehran University, 30 December 2017 AP Iran protests – in pictures A university student at a protest inside Tehran University while a smoke grenade is thrown by anti-riot Iranian police, 30 December 2017 AP Iran protests – in pictures University students at a protest inside Tehran University, 30 December 2017 AP Iran protests – in pictures University students run away from the police during an anti-government protest inside Tehran University, 30 December 2017 AP Iran protests – in pictures An image grab taken from a handout video released by Iran's Mehr News agency reportedly shows a group of men pulling at a fence in a street in Tehran, 30 December 2017 AFP/Getty Iran protests – in pictures Demonstrators gather to protest in Tehran, 30 December 2017 AP Iran protests – in pictures Iranians chant slogans as they march in support of the government near the Imam Khomeini grand mosque in Tehran, 30 December 2017 AFP/Getty Iran protests – in pictures Iranians chant slogans as they march in support of the government near the Imam Khomeini grand mosque in Tehran, December 30 2017 Iran protests – in pictures Iranian clerics take part during a state-organized rally against anti-government protests in the country, in the holy city of Qom, south west Iran, 3 January 2018 EPA Iran protests – in pictures In this photo provided by the Iranian Students' News Agency, a clergyman takes a picture of a pro-government demonstration in the southwestern city of Ahvaz, Iran, 3 January 2018 ISNA via AP Iran protests – in pictures Pro-government demonstrators gather at the Massoumeh shrine in Iran's holy city of Qom, some 130 kilometres south of Tehran, 3 January 2018 AFP/Getty

Iran’s army chief said police forces had already quelled anti-government unrest, but his troops were ready to intervene if needed as thousands took to the streets in support of the government in new state-sponsored rallies.

“Although this blind sedition was so small that a portion of the police force was able to nip it in the bud... you can rest assured that your comrades in the Islamic Republic’s army would be ready to confront the dupes of the Great Satan [United States],” state media quoted Major General Abdolrahim Mousavi as saying.

Following six days of demonstrations, the Revolutionary Guard said on Wednesday it had deployed forces to quell unrest in three provinces where most of the trouble had occurred, in the clearest sign authorities were taking the protests seriously.

The Revolutionary Guard were instrumental in suppressing an uprising over alleged election fraud in 2009 in which dozens were killed.

Pro-regime supporters in Iran take to the streets in State TV footage

In a letter to United Nations officials, the Iranian ambassador, Gholamali Khoshroo, complained Washington was intervening “in a grotesque way in Iran’s internal affairs”.

He said Mr Trump and his Vice President, Mike Pence, were personally stirring up trouble. “The President and Vice President of the United States, in their numerous absurd tweets, incited Iranians to engage in disruptive acts,” the ambassador wrote.

Mr Trump’s UN envoy, Nikki Haley, has called for an emergency Security Council meeting on Iran, saying the UN needed to speak out in support of the protesters. A meeting is yet to be scheduled.

Russia considers the proposal for an extraordinary meeting as “harmful and destructive”, Mr Ryabkov said in separate comments to Russia’s RIA news agency.