Protests continued on Tuesday against the Iranian government's announcement of a 50% increase in fuel prices on November 14th.
Video footage posted on social media showed clashes between protesters and security forces on the streets that left dozens dead and injured, as well as burning and vandalising some government buildings, facilities and banks, according to CNN.
Iran's Kayhan newspaper, supervised by Iranian leader Ayatollah Ali Khamenei, on Tuesday demanded the execution of demonstrators. Police in Tehran announced that a large number of demonstrators had been arrested, Al Arabiya television reported.
The UN Human Rights Office on Tuesday expressed concern that Iranian security forces were using live ammunition against protesters in violation of international law.
It urged the Iranian authorities to restore the Internet and respect the demonstrators' right to freedom of expression.
Iranian authorities on Monday had arrested more than 200 people and imposed restrictions on the use of the Internet.
Other Iranian news organisations across the country have indicated that the number of detainees reached one thousand, according to the newspaper Asharq al-Awsat.
The fourth day of the Iranian protests on Monday evening was bloody, with more than 45 demonstrators killed, as well as the deaths of a number of security elements, Revolutionary Guards and Basij militia members.
The governor of Tehran said that the protests were widespread in 22 out of 31 Iranian provinces, or 70% of the country.
Demonstrations began Friday after the announcement of a 50% price increase for the first 60 litres of gas and 200% for each additional litre purchased each month.
Iran's economy has been in crisis since May last year, when Trump pulled out of a nuclear deal signed in 2015 and reimposed tough sanctions on Tehran.
Local sources said that the Iraqi Popular Mobilization militias participated with the Revolutionary Guards in the Basij to suppress the demonstrations south of Ahwaz Monday, where 12 demonstrators were killed and four others were injured.
Three demonstrators were also killed in the nearby city of Koura, and at least 30 protesters were killed in violent clashes between the demonstrators and the Basij militias and Iranian security forces in the cities of Maashour, Sarbandar, Al-Mahara, Abadan and Al-Falahia, located south of Ahwaz province.
Iranian opposition leader Maryam Rajavi described the international community's inaction towards the unrest as unacceptable.
She said the death toll had reached more than 200 and the number of detainees was much higher than what the Revolutionary Guards announced.
US Secretary of State Mike Pompeo said on Monday that Washington was deeply concerned about reports of deaths in Iran's protests. The United States on Sunday also condemned Iran's use of "lethal force" against demonstrators.
Given the developments on the ground, the situation in Iran appears to be deteriorating quickly. A number of analysts believe that Tehran's existing regime is not viable.
Some believe that the regime will not fall permanently because of these demonstrations, but may enter a very stalled phase which will change its future.
Political writer Dr Amr Al-Shobaki said that the Iranian demonstrations may not bring down the regime, but could prompt a radical review of its policies at home and abroad.