Iran's Foreign Minister Mohammad Javad Zarif ridiculed US President Donald Trump on Saturday over what he called the foreign policy "blunder" of trying to raise its recent protests at the UN Security Council.

The Security Council "rebuffed the US' naked attempt to hijack its mandate", Zarif wrote on Twitter.

"Majority emphasised the need to fully implement the JCPOA (nuclear deal) and to refrain from interfering in internal affairs of others. Another FP (foreign policy) blunder for the Trump administration."

It came as an Iranian politician said some 90 students were arrested in Tehran during last week's unrest.

"According to the figures and information obtained by officials at the Ministry of Higher Education, the majority of those arrested were basically not involved in the protests and most were arrested outside the university," Mahmoud Sadeghi, an outspoken member of parliament, told the reformist ILNA news agency.

"Some were arrested in front of the doors of their houses," he added.

Saturday saw a fourth straight day of pro-government rallies in smaller cities as the regime sought to emphasise the end of five days of unrest that claimed 21 lives and saw hundreds arrested around the country.

The protests began on December 28 as protests over economic hardship and quickly turned against the regime as a whole.

Protests in Tehran were focused around the university but were relatively small compared to other towns and cities, with only a few hundred taking part.

A police spokesman said most of those arrested "had been duped" into joining the protests and had now been freed under caution, according to state news agency IRNA.

"However, the leaders of the troubles are in the hands of the judiciary and in prison," he added.

- 'A waste of time' -

At the United Nations, Washington saw allies and rivals push back against the Security Council meeting it had called to discuss the unrest in Iran.

US Ambassador Nikki Haley argued that the unrest could escalate into full-blown conflict and drew a comparison with Syria.

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

But Russia's envoy shot back that if the US view holds, the council should have also discussed the 2014 unrest in the US suburb of Ferguson, Missouri, over the police shooting of a black teenager or the US crackdown on the Occupy Wall Street movement.

Britain and France reiterated that Iran must respect the rights of protesters, but French Ambassador Francois Delattre said the "events of the past days do not constitute a threat to peace and international security".

China also described the meeting as meddling in Iran's affairs, while Ethiopia, Kuwait and Sweden expressed reservations about the discussion.

Iran's Ambassador Gholamali Khoshroo slammed the meeting as a "farce" and a "waste of time", and said the council should instead focus on addressing the Israeli-Palestinian conflict or the war in Yemen.

Iran signed a nuclear deal with the United States, Britain, France, Germany, Russia and China in 2015, easing sanctions in exchange for curbs to the country's nuclear programme.

Trump has fiercely opposed the deal, but the other signatories remain firmly behind it.

He must decide every few months whether to continue waiving nuclear sanctions, with the next deadline due on Friday.

Analysts say there is a chance he may use the latest unrest as a pretext to reimpose sanctions.