At least three children are reported to have been killed and more than 40 minors arrested after eight days of the ongoing protests across Iran, as human rights groups accuse the regime’s security forces of “indiscriminate targeting of civilians”.

The nationwide uprising sparked by the collapse of the country’s currency and rising living costs has spread to at least 78 cities and 222 locations, with demonstrators calling for the end of the regime, according to the US-based Human Rights Activists in Iran (HRAI).

The protests continued over the weekend despite a worsening crackdown by security forces after comments from the country’s supreme leader, Ali Khamenei, who addressed protesters as “rioters”. So far, 990 people have been arrested and at least 20 killed, according to HRAI.

Among the minors reportedly killed was Mostafa Falahi, a 15-year-old from the city of Azna, in central Iran. The Oslo-based Hengaw Organization for Human Rights said Falahi had been killed when security forces opened fire on protesters on 1 January. The group also reported the death of another minor, 17-year-old Rasul Kadivarian, who was killed along with his 20-year-old brother, Reza, on 3 January when security forces fired directly on protesters in the city of Kermanshah.

A third child, a 17-year-old whose death was reported by state media in the city of Qom, in central Iran, has also been confirmed by human rights groups, who said their identity had yet to be verified.

Skylar Thompson, deputy director of HRAI, told the Guardian the group had documented the killings, as well as the arrests of at least 44 children.

“These numbers provide clear evidence that youth are present throughout the ongoing protests. The indiscriminate targeting of a civilian population must be widely condemned as a violation of international law, especially with the clear illustration of children present,” Thompson said.

During the Woman, Life, Freedom protests in Iran in 2022 more than 500 people were reportedly killed, including at least 60 children, some as young as eight years old.

Speaking on the condition of anonymity, a witness from the district of Malekshahi, in Ilam, western Iran, said crowds over the weekend had been chanting anti-government slogans and demanding the release of protesters already detained.

“We then gathered in front of a government building. That was when the forces opened fire on us. It felt as if they were shooting at enemies or armed groups. I felt like I was in a war zone. I saw several people injured, and I believe some were killed on the spot. We tried to take the wounded to hospitals and prevent government forces from arresting injured protesters,” the witness said.

Human rights groups reported late Saturday and Sunday night that the security forces had raided and attacked the Khomeini hospital in the city of Ilam, western Iran, where injured protesters had been taken.

Awyar Shekhi from Hengaw, said: “State forces are firing directly at gatherings and protests without regard for whether those targeted are children or adults. The crackdowns are brutal: teargas and military-grade weapons are being used, and detainees are severely beaten before being transferred to undisclosed locations.”

Another witness from Qom said the security forces could see there were teenagers and children among the protesters, “but that didn’t stop them from firing pellets, teargas and gunfire. The whole situation is only getting more deadly.”