Iranian authorities cut internet access in Khuzestan province and deployed security forces in several cities as fresh anti-government protests broke out against the regime on Thursday.
Security forces fired tear gas to disperse protesters in the city of Behbahan in the oil-rich south-western province, witnesses told Reuters.
The internet monitoring group NetBlocks reported network disruptions in Khuzestan from 10pm on Thursday that "affect connectivity at the network layer and cannot be worked around by users. Hence, they are likely to significantly limit coverage of incidents as they take place."
Videos posted on social media from inside Iran showed protesters chanting, "Fear not, fear not, we are in this together".
Others showed a heavy presence of security forces in Tehran and Isfahan. Some protesters chanted slogans against top officials.
"People are angry. The economy is so bad that we cannot survive," an Iranian man from Tehran told Reuters by telephone.
Witnesses in Behbahan said there had been several arrests in the city, which is in Iran's oil-rich Khuzestan province.
Behbahan’s police chief, Col Mohammad Azizi, later was quoted by Iranian website jamaran.news as confirming a protest took place beginning at 9pm. He said police “firmly dispersed” the demonstrators, who rallied over the economy, and there there were no injuries.
The police issued a statement on Friday urging people to "vigilantly refrain from any gathering that could provide a pretext for the counter-revolutionary movement", accusing "enemies" of whipping up discontent.
"The police force has an inherent and legal duty to deal decisively with these desperate moves," the statement said.
Iran's Supreme Court this week upheld the death penalty against Amirhossein Moradi, Saeed Tamjidi and Mohammad Rajabi over protests last November sparked by a rise in petrol prices.
A group of UN rights experts called on Iran to overturn the death sentences and said the men were tortured and coerced into making confessions.
"Today we join hundreds of thousands of Iranians on social media who condemned these death sentences," said the group of more than a dozen independent UN experts.
Last year's unrest began with protests over economic hardship but turned political, with demonstrators demanding top officials step down. Authorities responded by cutting off internet access and sending out security forces to quell the protests.
Iran's interior ministry said in May that 225 people were killed during the protests, including security forces, but the US has alleged that the actual number is far higher.
The upholding of the death penalties on Tuesday prompted calls on social media for protests across the country on Friday.
Iran's Tasnim news agency said the security forces had arrested "key elements of opposition groups... who were encouraging people to protest on Friday in the north-eastern Khorasan Razavi province".
Additional reporting from Reuters