Iran has disrupted internet access to the outside world as angry demonstrators rallied over the collapse of a tower in Iran that has killed at least 36 people, experts said.

The disruption plunged the south-western province into digital isolation, making it difficult for journalists to authenticate events on the ground and for activists to share footage and organise protests.

It is a tactic the Iranian government has repeatedly employed during times of unrest, rights activists say, in a country where radio and television stations already are state-controlled and journalists face the threat of arrest.

The internet interference in the oil-rich Khuzestan province started in early May, weeks before the fatal collapse, said Amir Rashidi, director of internet security and digital rights at Miaan Group, which focuses on digital security in the Middle East.

The province, home to an ethnic Arab population that long has alleged discrimination, was a flashpoint in protests over the sinking economy and skyrocketing prices of food staples.

Disruptions then intensified in the area after the Metropol Building collapse last week, according to data shared by the Miaan Group.

Iran Building Collapse
Debris hangs from the Metropol building in the south-western city of Abadan, Iran (Hossein Abdollah Asl, Tasnim News Agency via AP)

The disaster ignited widespread anger in Abadan, where residents alleging government negligence gathered nightly at the site of the collapse to shout slogans against the Islamic Republic.

Videos of the protests have circulated widely online, with some showing officers clubbing and firing tear gas at demonstrators.

The footage analysed by The Associated Press corresponded to known features of Abadan, some 410 miles south-west of the capital, Tehran. The number of casualties and arrests remains unclear.

In response to the protests, Iranian authorities at times completely shut down the internet and other times allowed only tightly controlled use of a domestic Intranet, reported the Miaan Group.

During the day, authorities also appear to have restricted bandwidths to make it very difficult for people to share large files, such as video, without leaving Abadan altogether, said Mahsa Alimardani, a senior researcher at Article 19, an international organisation that fights censorship.

Last Friday, as massive crowds took to the streets to chant against top officials, a digital barricade of sorts went up between Iran and the world, data showed. Only certain government-approved national websites could stream content but not websites based abroad.

“There has been a pattern that we’ve seen when it gets dark where Google isn’t working but the website of the Supreme Leader is working well,” Mr Rashidi said.

The Iranian mission at the United Nations did not immediately respond to request for comment.

Meanwhile, rescue workers pulled more bodies from the rubble on Tuesday, taking the death toll to 36 amid fears more people could be trapped in the ruins.

Five of the victims were school-age children, the official IRNA news agency reported. Another 37 people were injured in the collapse, with two still in hospital.

Officials have blamed the building’s structural failure on shoddy construction practices, lax regulation and entrenched corruption, raising questions about the safety of similar towers in the earthquake-prone country.

Authorities reported they evacuated residents from buildings near the disaster site, fearing structural damage.