Street protests over water shortages in southwest Iran continued for a sixth night on Tuesday amid rising violence, while residents in the capital of Tehran chanted anti-government slogans, according to videos posted on social media and Iranian news outlets.

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

After various opposition groups and activists called for demonstrations to support the Khuzestan protesters, videos, which surfaced on late Tuesday and early Wednesday, showed women chanting "Down with the Islamic Republic" at a Tehran metro station. At night, some people in the capital vented their anger with chants against Supreme Leader Ayatollah Ali Khamenei.

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

Iran is facing its worst drought in 50 years and the water crisis has affected households, agriculture, and livestock farming, and led to power blackouts.