The Kurdish-populated provinces of western and northwestern Iran have been major hubs of protest since the onset of the movement sparked by the death in September of young Kurdish woman Mahsa Amini, who had been arrested by morality police in Tehran.

There have been particularly intense anti-regime demonstrations in several towns in the last few days, largely sparked by the funerals of people said to have been killed by the security forces in previous protests.

The Norway-based Hengaw rights group said Iranian forces had shelled overnight the cities of Piranshahr, Marivan and Javanroud, posting videos with the thud of heavy weaponry and sound of live gunfire.

It said 13 people had been killed in the region by the security forces over the last 24 hours, including seven in Javanroud, four in Piranshahr and two more in other locations.

Among six people killed by fire from the security forces on Sunday was 16-year-old Karwan Ghader Shokri, Hengaw said.

Another man was killed when security forces fired on crowds as the teenager's body was being brought to the mosque, it added.

AFP could not immediately verify the toll.

Hengaw said that amid "intense confrontations" between protesters and security forces in Javanroud, there was now a shortage of blood for the wounded in its hospitals.

- 'Intensifying violence' -

The latest violence came amid continued concern over the situation in Mahabad, where rights groups said security forces had sent reinforcements the day before to press a crackdown.

"Greatly concerned that Iranian authorities are reportedly escalating violence against protesters, particularly in the city of Mahabad," US Secretary of State Antony Blinken wrote on Twitter.

"We continue to pursue accountability for those involved, as we support the Iranian people," he added.

The Norway-based Iran Human Rights (IHR) group also posted footage it said showed security forces using live fire against protesters in Piranshahr.

It also showed the distraught mother of the 16-year-old Karwan Ghader Shokri prostrating herself on his corpse as it was taken for burial.

"Mother, don't cry, we will take revenge," the mourners chanted in Kurdish, the rights group said.

IHR's director Mahmood Amiry-Moghaddam posted a video showing wounded protesters lying in the street in Javanroud, surrounded by the constant sound of gunfire.

"They are intensifying the violence against defenceless citizens," he wrote on Twitter.

People also took to the streets in Kermanshah, a Kurdish-populated provincial capital, chanting "death to (supreme leader Ayatollah Ali) Khamenei", another video posted by IHR said.

The protests sparked by Amini's death have become the most serious challenge to the Iranian regime since the 1979 revolution.

Analysts have noted a trend of violence by the security forces has simply triggered more protests, with large crowds turning out for funerals and 40-day "chehelom" mourning ceremonies.

Kurds make up one of Iran's most important non-Persian ethnic minority groups and generally adhere to Sunni Islam rather than the Shiism dominant in the country.

Amid the crackdown, Iran renewed cross-border missile and drone strikes overnight into Monday in neighbouring Iraq against Kurdish opposition groups it accuses of stoking the protests.

The latest Iranian strikes also come a day after Turkey carried out air raids against outlawed Kurdish militants in Iraqi Kurdistan and northern Syria.