US ambassador to the United Nations Nikki Haley sought a meeting of the top UN body to show support for demonstrators in Iran. Photo: AFP/Drew Angerer 

The United States and Russia clashed over Iran at the UN Security Council on Friday as a third straight day of pro-regime rallies were held following a wave of deadly protests.

US Ambassador Nikki Haley pushed for the meeting of the top UN body, arguing the unrest could escalate into full-blown conflict and drawing a comparison with Syria.

"The Iranian regime is now on notice: the world will be watching what you do," Haley warned.

Russia opposed the US push for Iran to be discussed at the Security Council, arguing the protests pose no threat to international peace and security.

But Moscow stopped short of seeking to block the meeting.

A total of 21 people have died and hundreds have been arrested since December 28 as protests over economic woes turned against the regime as a whole, with attacks on government buildings and police stations.

Pro-regime rallies were held around Tehran Friday for the third day running with authorities seeking to put a lid on the violence. There were some reports of small anti-government demonstrations in provincial towns, but these could not be verified.

"We obviously regret the loss of life as the result of demonstrations that weren't so peaceful," Russian Ambassador Vassily Nebenzia told the council.

"However, let Iran deal with its own problems," he said.