The European Union has said it was weighing tough new sanctions on Iran over a lethal crackdown on protests sparked by the "killing" of Mahsa Amini, after a similar move by the United States.

Ms Amini, 22, was pronounced dead on 16 September, days after the notorious morality police detained the Kurdish Iranian for allegedly breaching rules requiring women to wear hijab headscarves and modest clothes.

Anger over her death has sparked the biggest wave of protests to rock Iran in almost three years and a crackdown that has seen scores of protesters killed and hundreds arrested.

EU foreign policy chief Josep Borrell said the bloc was considering "all the options at our disposal, including restrictive measures, to address the killing of Mahsa Amini and the way Iranian security forces have been responding to the demonstrations".

It came after US President Joe Biden said the United States would impose "further costs" this week on "perpetrators of violence against peaceful protesters" in Iran.

Rights groups voiced deep concern after Iranian riot police used tear gas and paintball guns against hundreds of students at Tehran's Sharif University of Technology on Sunday night, with video footage showing detainees being taken away with fabric hoods over their heads.

Protests also spread to schools, with video footage shared by Kurdish rights group Hengaw showing schoolgirls demonstrating in two cities in Ms Amini's native Kurdistan province.

Mr Biden gave no indication of what measures he was considering against Iran, which is already under crippling US economic sanctions largely related to its controversial nuclear programme.

Iran has accused the US leader of "hypocrisy" in invoking human rights to impose fresh punitive measures.

"It would have been better for Mr Joe Biden to think a little about the human rights record of his own country before making humanitarian gestures, although hypocrisy does not need to be thought through," foreign ministry spokesman Nasser Kanani said in an Instagram post, reported by Iranian media.

Iran's supreme leader Ayatollah Ali Khamenei had yesterday accused arch foes the United States and Israel of fomenting the protests.

The riots "were engineered by America and the occupying, false Zionist regime, as well as their paid agents, with the help of some traitorous Iranians abroad", Mr Khamenei said.

The unrest has overshadowed diplomatic efforts to revive a 2015 nuclear deal between Iran and major powers which had come close to a breakthrough in recent months before stalling again.

But White House press secretary Karine Jean-Pierre stressed the "problems with Iran's behaviour" are separate from efforts to revive the nuclear deal, which Washington will pursue "as long as we believe" it is in US national security interests.

In his first public comments on Ms Amini's death, 83-year-old Khamenei stressed yesterday that Iranian police must "stand up to criminals".

Mr Khamenei said "some people, without proof or an investigation, have made the streets dangerous, burned the Koran, removed hijabs from veiled women and set fire to mosques and cars".

He added that "this is not about hijab in Iran", and that "many Iranian women who don't observe the hijab perfectly are among the steadfast supporters of the Islamic republic".

Another 400 people arrested in the crackdown were released today "on condition of not repeating their actions", Tehran prosecutor Ali Salehi said, quoted by state news agency IRNA.

Iran has repeatedly accused outside forces of stoking the protests and last week said nine foreign nationals - including from France, Germany, Italy, the Netherlands and Poland - had been arrested.

At least 92 protesters have been killed so far in the Mahsa Amini rallies, said Oslo-based group Iran Human Rights, which has been working to assess the death toll despite internet outages and blocks on WhatsApp, Instagram and other online services.

Amnesty International said earlier it had confirmed 53 deaths, after Iran's semi-official Fars news agency said last week that "around 60" people had died.

At least 12 members of the security forces have been reported killed since 16 September.