A wave of protests sparked by Iran’s failing economy has continued for a ninth day, as President Donald Trump renewed his threat of US intervention.

Videos published online on Monday showed demonstrations in the capital, Tehran, and the south-western city of Yasuj.

Human rights activists have said protests have taken place in 26 of the country’s 31 provinces since last week, and that at least 19 protesters and one member of the security forces have been killed.

Trump warned on Sunday night that Iranian authorities would be “hit very hard” if more protesters died.

“We’re watching it very closely. If they start killing people like they have in the past, I think they’re going to get hit very hard by the United States,” he told reporters on Air Force One.

On Monday, Iran’s judiciary chief, Gholamhossein Mohseni Ejei, said authorities would “listen to protesters and critics who legitimately and rightly have concerns about their livelihood and social and economic welfare”.

But he added that they would “deal firmly with those who seek to exploit the situation, incite riots, and undermine the security of the country and the people”.

“Rioters must know there will be no leniency or appeasement towards them,” he warned.

The Iranian foreign ministry’s spokesman also accused Israel of seeking to “undermine our national unity”, after Prime Minister Benjamin Netanyahu expressed his government’s “solidarity with the struggle of the Iranian people” on Sunday.

Esmail Baqai told a news conference that the statements by Netanyahu and “certain radical American officials” were “nothing more than incitement to violence”.

Iran and Israel fought a 12-day war last June, during which Israeli and US jets bombed key Iranian nuclear facilities.

The latest protests in Iran began when shopkeepers took to the streets of Tehran on 28 December to express their anger at another sharp fall in the value of the Iranian currency against the US dollar. The rial has sunk to a record low and inflation has risen to 40% as sanctions over Iran’s nuclear programme squeeze the economy.

University students soon joined the protests and they began spreading to other cities.

On Monday, footage posted on social media appeared to show a protest in the city of Yasuj, in Kohgiluyeh-Boyer Ahmad province, according to BBC Persian. A crowd of men and women could be heard chanting “Freedom, freedom, freedom”.

Protesters were also filmed chanting the same slogan around Cheragh Barq street in Tehran.

Videos obtained by BBC Persian on Sunday night appeared to show several dozen protesters marching down a street in the city of Sari, north of Tehran.

They can be heard chanting slogans including “Death to the dictator” – a reference to Khamenei, who has ultimate power in the country – and “Pahlavi is coming back” – a reference to Reza Pahlavi, the exiled son of the late shah.

In another clip, a number of people are seen fleeing amid the sound of gunfire.

BBC Persian said there were also protests in the districts of Ilam, Arak, Hamedan, Amol, Lahijan, Kermanshah, Malekshahi, Semnan and Noorabad on Sunday evening.

Another video purportedly showed security forces storming a hospital in the western city of Ilam, where a human rights activist said wounded protesters were sheltering.

Kurdish human rights group Hengaw reported that the protesters were among those shot when Revolutionary Guards opened fire on a demonstration outside a government compound in neighbouring Malekshahi county on Saturday

Four other protesters were killed in the incident, Hengaw added, identifying one of them as retired Revolutionary Guards brigadier-general Latif Karimi. It shared a video that appeared to show a crowd banging on a gate before shots ring out and people fall to the ground.

The semi-official Mehr and Tasnim news agencies reported that three people – including Karimi, whom they said was a member of the security forces – were killed when “rioters” tried to enter a security facility.

Iran’s Human Rights Activists News Agency (HRANA) said on Sunday night a total of 19 protesters and one person affiliated with the security forces had been killed during the unrest.

Another 51 people had been injured, mostly by birdshot and plastic bullets, and 990 people had been arrested in connection with the protests, it added.

The protests have been the most widespread since an uprising in 2022 sparked by the death in custody of Mahsa Amini, a young Kurdish woman who was detained by morality police for allegedly not wearing her hijab properly.

More than 550 people were killed and 20,000 detained in a violent crackdown on those protests by security forces, according to human rights groups.