Protesters angry about water shortages took to the streets of southwest Iran for a sixth night in a row on Tuesday, with mounting violence, while Tehran residents chanted anti-government slogans, according to videos posted on social media on Wednesday and Iranian news outlets.

Videos uploaded by social media users showed security forces using teargas to disperse protesters. The semi-official Fars news agency said“rioters” shot dead one policeman and injured another in the port city of Mahshahr in oil-rich Khuzestan province.

In the town of Izeh, demonstrators chanted“Reza Shah, bless your soul” in a video, referring to the founder of the Pahlavi dynasty which was overthrown by the 1979 Islamic Revolution.

Activists called for demonstrations to support the Khuzestan protesters and videos surfaced late Tuesday and early Wednesday showing women chanting“Down with the Islamic Republic” at a Tehran metro station.

Reuters could not independently authenticate the videos.

At least two young men have been shot dead in the protests. Officials have blamed armed protesters, but activists said on social media they were killed by security forces.

Iran's ethnic Arab minority, who mostly live in Khuzestan, have long said they face discrimination. An Arab woman protester could be heard shouting at security forces in one video:“Sir! Sir! The demonstration is peaceful. Why do you shoot? No one took your land and water.”

Iran's worst drought in 50 years has triggered power blackouts.

Iran's economy has been blighted by sanctions imposed by former U.S. President Donald Trump, and the COVID-19 pandemic. Workers, including thousands in the key energy sector, and pensioners have protested for months amid discontent over mismanagement, unemployment and inflation.

In Washington, U.S State Department spokesman Ned Price said the United States was closely following the protests, including reports that security forces had fired on protesters.

”We support the rights of Iranians to peacefully assemble and to express themselves. Iranians ... should enjoy those rights without fear of violence, without fear of arbitrary detention by security forces,” he told reporters.

At least 31 protests took place across Iran on Monday and Tuesday, including rallies by workers and farmers, according to the dissident Human Rights Activists News Agency.