DUBAI: A fire at Iran's Evin prison late on Saturday killed four detainees and injured 61, state media reported, as anti-government protests sparked by a woman's death in police custody continued on Sunday, including at several universities.

Iranian authorities said on Saturday that a prison workshop had been set on fire "after a fight among a number of prisoners convicted of financial crimes and theft". Evin also holds many detainees facing security charges, including Iranians with dual nationality.

Iran's judiciary said four of those injured in Saturday's fire were in critical condition and that those killed had died of smoke inhalation, Iranian state media reported.

Protests sparked by 22-year-old Mahsa Amini's death on Sept. 16 have turned into one of the boldest challenges to Iran's clerical rulers since the 1979 revolution, with protesters calling for the downfall of the Islamic Republic, even if the unrest does not seem close to toppling the system.

Demonstrations continued at several universities on Sunday, including in the cities of Tabriz and Rasht, to a heavy deployment of riot police. Videos posted on social media showed students at a Tehran university chanting: "Iran has turned into a big prison. Evin prison has become a slaughterhouse."

Other videos showed fires being lit at road intersections in several cities, including the capital and Piranshahr in the west of the country, where car drivers honked their horns and anti-government slogans could be heard.

Dozens of protesters were also seen in a poor neighbourhood of Tehran, before being dispersed by security forces mounted on motorbikes and shooting tear gas cannisters in the air.

Reuters could not independently verify the videos.

Families of some political detainees took to social media to call on the authorities to ensure their safety at Evin prison, which in 2018 was blacklisted by the U.S. government for "serious human rights abuses".

Footage of the prison aired on state television hours after the fire apparently showed that calm had returned to the facility with inmates asleep in their wards. It also showed firefighters inspecting a workshop with fire damage to the roof.

Atena Daemi, a human rights activist, said that relatives of prisoners in the women's section had gone to Evin for visiting hours, but authorities denied them access, resulting in a standoff. Prisoners were "fine, but the phones are broken", they were told, according to Daemi. She later tweeted that some women prisoners had called their families.

The husband of Iranian journalist Niloofar Hamedi, who broke the news of Amini's hospitalisation and was arrested last month, also wrote on Twitter that she had telephoned him on Sunday.

A lawyer representing an American Iranian held at Evin, Siamak Namazi, imprisoned for nearly seven years on espionage-related charges rejected by Washington as baseless, said on Sunday that Namazi had contacted his relatives.

"SiamakNamazi has now spoken to his family. He is safe and has been moved to a secure area of Evin Prison. We have no further details," lawyer Jared Genser said in a tweet.

Several other dual national Iranians and foreign citizens are held in Evin prison mostly for security-related charges. Some Twitter posts by their friends and relatives said they had contacted their families on Sunday.

VIOLENT CRACKDOWN

Asked about the prison fire, U.S. President Joe Biden said on Saturday he was surprised by the courage of Iranian protesters. He earlier called on Iran "to end the violence against its own citizens simply exercising their fundamental rights".

Iran's President Ebrahim Raisi said Biden was inciting "chaos, terror, and destruction... (and) should be reminded of the eternal words of the founder of the Islamic Republic who called America the great satan," referring to Iran's late revolutionary leader Ayatollah Ruhollah Khomeini.

France's foreign ministry said on Sunday it was following with the utmost attention the situation at Evin prison, "where several French nationals are being arbitrarily detained".

Protests have been met with a brutal state crackdown. Rights groups said at least 240 protesters had been killed, including 32 minors. Over 8,000 people had been arrested in 111 cities and towns, Iranian activist news agency HRANA said on Saturday. The authorities have not published a death toll.

Among the casualties have been teenage girls whose deaths have become a rallying cry for more demonstrations across the country.

Iran, which has blamed the violence on enemies at home and abroad, denies security forces have killed protesters. State media said on Saturday at least 26 members of the security forces had been killed by "rioters".