President Joe Biden said Monday the United States would impose “further costs” on Iran for its violent crackdown on nationwide protests sparked by outrage over the death of Mahsa Amini.

Amini, 22, was pronounced dead on September 16, days after the notorious morality police arrested the Kurdish Iranian for allegedly breaking rules forcing women to wear hijab headscarves and modest clothing.

Anger over her death has sparked the biggest wave of protests in Iran in nearly three years, with security forces cracking down on hundreds of university students in Tehran on Sunday night.

“This week, the United States will continue to impose additional costs on perpetrators of violence against peaceful protesters,” Biden said in a statement.

“We will continue to hold Iranian officials accountable and support Iranians’ right to protest freely.”

Biden added he was “deeply concerned” by reports of increasing crackdown on protesters and said Washington stands “with all the citizens of Iran who are inspiring the world with their courage.”

Biden did not provide any information on what measures he is considering. Iran is already under crippling US economic sanctions, largely related to its controversial nuclear program.

White House press secretary Karine Jean-Pierre stressed earlier Monday that “problems with Iran’s conduct” were separate from efforts to revive the 2015 nuclear deal, which Washington will pursue “as long as we believe” that it is in the interests of US national security.

Iran’s supreme leader Ayatollah Ali Khamenei had accused arch-enemies the USA and Israel of fueling the upheaval.

The riots “were orchestrated by America and the occupying false Zionist regime and their paid agents with the help of some traitorous Iranians abroad,” the Islamic Republic leader said.

In his first public comments on Amini’s death, 83-year-old Khamenei stressed that the police “must stand up to criminals”.

Khamenei said “some people, without any evidence or investigation, have made the streets dangerous, burned the Koran, removed hijabs from veiled women, and set mosques and cars on fire.”

He added that “this is not about hijab in Iran” and that “many Iranian women who are not perfectly observant of hijab are among the staunch supporters of the Islamic Republic”.

Concerns grew over a night crackdown on students at Tehran’s prestigious Sharif University of Technology, where local media reported riot police used steel ball guns, tear gas and paintball guns against hundreds of students.

“Woman, life, freedom” shouted the students, “students prefer death to humiliation,” reported the news agency Mehr.

The Oslo-based group Iran Human Rights released videos that appear to show police officers on motorcycles chasing students running through an underground parking lot and picking off detainees whose heads are covered with black cloth bags.

In a clip recorded at a Tehran subway station, according to IHR, a crowd can be heard shouting, “Don’t be afraid! Have no fear! We are all together!”

Federal Foreign Minister Annalena Baerbock said of the protests at the universities that the courage of the Iranians was “incredible” and that the “regime’s brute force was an expression of sheer fear of the power of education and freedom”.

British Foreign Secretary James Cleverly said the violence against protesters was “truly shocking” and called Tehran’s top diplomats to London, while Canada imposed new sanctions and spearheaded “the outrageous actions of Iran’s so-called ‘moral police'”.

Protests were also reported at other universities, including downtown Isfahan.

Iran has repeatedly accused outside forces of fueling the protests and said last week nine foreigners – including those from France, Germany, Italy, the Netherlands and Poland – had been arrested.

The parents of Italy’s Alessia Piperno, 30, from Rome, said they lost touch with her after speaking to her on Wednesday – her birthday – but then received a call from her on Sunday, apparently from custody.

“I’m fine, but there are people here who say they’ve been inside for months and for no reason,” she told them, according to Il Messaggero, Rome’s daily newspaper. “I’m afraid I won’t be let out again. Help me.”

Italy’s Foreign Ministry has not yet commented on the identity of the arrested Italian.

At least 92 protesters have been killed at Mahsa Amini rallies so far, said the IHR, which has been working to establish the death toll despite internet outages and suspensions of WhatsApp, Instagram and other online services.

Amnesty International previously said 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 killed since September 16.