The Iranian province of Khuzestan has experienced internet outages amid demonstrations over a water shortage, NetBlocks says.
Mobile internet services in Iran have been disrupted amid ongoing protests against a water crisis in the country's southwest.
At least three people -- including a police officer -- have been killed in clashes in Khuzestan, state media have reported.
Demonstrators have been calling for action to address the shortage of water in the oil-rich province for seven consecutive days.
Iran's authorities have blamed the water crisis on a severe drought, noting that rainfall in the region has decreased by almost 50% in the last year, leaving dams with dwindling water supplies.
But citizens in Khuzestan -- a province home to a large Arab minority -- have repeatedly complained that they are being left behind by the Iranian regime.
Prominent lawyers have said that Khuzestan’s problem stems from the illegal theft of water from river forks in the region. Outgoing Iranian President Hassan Rouhani has described the protests as a "natural right".
Hashtags in Farsi and Arabic such as #KhuzestanIsThirsty and #KhuzestanHasNoWater have been widely used on social media to direct attention towards the crisis and protests.
On Thursday, the internet monitoring observatory NetBlocks confirmed there had been a "significant regional disruption" to mobile internet service since last week.
Cities in the region, including Ahvaz, Ramhormoz, and Susangerd, had experienced "a severe slowing of internet service or near-total internet shutdown" since 15 July, NetBlocks said in a statement.
"[This] is likely to limit the public’s ability to express political discontent or communicate with each other and the outside world."
The organisation added that cellular data analysis indicated the regional shutdown "intended to control protests".
Although fixed-line and WiFi connectivity remained stable in the Khuzestan, Net Blocks noted that the area is reported to be "highly dependent" on mobile data services.
Iran has faced a series of network disruptions, including during widespread public protests against rising fuel prices in November 2019.
State authorities accused of "acts of violence"
Despite the internet shutdowns, multiple videos have emerged online of shots being fired and tear gas being used by the authorities against demonstrators in Iran.
The Human Rights Activists in Iran group submitted an open letter, signed by more than 130 documentarians, calling on Tehran to end "acts of violence" on citizens.
"We stand by the thirsty people of Khuzestan and strongly condemn the repression of the people," the letter read.
"As nearly five million Iranians in Khuzestan are lacking access to clean drinking water, Iran is failing to respect, protect, and fulfill the right to water, which is inextricably linked to the right to the highest attainable standard of health."
Iran has in the past blamed "rioters" for deaths occurring amid heavy-handed crackdowns by security forces.
On Wednesday, state media reported that an Iranian police officer was killed during unrest, raising the death toll in the unrest to at least three people.
U.S. State Department spokesman Ned Price has told journalists that Washington was following closely reports that Iranian security forces had fired on protesters.
The rallies in Khuzestan come as Iran struggles through repeated waves of infections in the coronavirus pandemic and as thousands of workers in its oil industry have launched strikes for better wages and conditions.
Iran's economy also has struggled under US sanctions since former President Donald Trump's 2018 decision to unilaterally withdraw from Tehran's nuclear deal.