Protesters angry over a building collapse in south-west Iran that killed at least 31 people shouted down an emissary sent by the supreme leader, Ayatollah Ali Khamenei, prompting a crackdown in which riot police clubbed demonstrators and fired teargas, according to online videos. The protest directly challenged the Iranian government’s response to the disaster a week ago as pressure rises in the Islamic Republic over rising food prices and other economic woes amid the unravelling of its nuclear deal with world powers. While the protests so far appear to be leaderless, Arab tribes in the region seemed to join them on Sunday, raising the risk of the unrest intensifying. Already, tensions between Tehran and the west have risen after Iran’s paramilitary Revolutionary Guards on Friday seized two Greek oil tankers. Ayatollah Mohsen Heidari AleKasir tried to address mourners near the site of the 10-storey Metropol building in the city of Abadan but the hundreds gathered there booed and shouted. Surrounded by bodyguards, the ayatollah, who is in his 60s, tried to continue but could not. “What’s happening?” the cleric asked a bodyguard, who then leaned in to tell him something. The cleric tried to address the crowd again: “My dears, please keep calm, as a sign of respect to Abadan, its martyrs and the dear [victims] the whole Iranian nation is mourning tonight.” The crowd responded by shouting: “Shameless!” A live broadcast of the event on state television then cut out. Protesters later chanted: “I will kill, I will kill the one who killed my brother!” The Tehran-based daily newspaper Hamshahri and the semiofficial Fars news agency said the protesters attacked the platform where state TV had set up its camera, cutting off its broadcast. Police ordered the crowd not to chant slogans against the Islamic Republic and ordered them to leave, calling their rally illegal. Video later showed officers confronting and clubbing protesters as clouds of teargas rose. At least one officer fired what appeared to be a shotgun, though it was not clear if it was live fire or so-called “beanbag” rounds designed to stun. It was not immediately clear if anyone was injured or if police made any arrests. The details in the videos analysed on Monday corresponded to known features of Abadan, 410 miles (660km) south-west of the capital, Tehran. Foreign-based Farsi-language television channels described teargas and other shots being fired. Independent newsgathering remains extremely difficult in Iran. During unrest, Iran has disrupted internet and telephone communications to affected areas, while also limiting the movement of journalists inside the country. Reporters Without Borders has described Iran as the third-worst country in the world to be a journalist – behind only North Korea and Eritrea. After the tower collapse in Abadan last Monday, authorities acknowledged the building’s owner and corrupt government officials had allowed construction to continue despite concerns over shoddy workmanship. Authorities have arrested 13 people as part of an investigation into the disaster, including the city’s mayor. Rescue teams pulled two more bodies from the rubble on Monday, bringing the death toll to 31, according to the state-run IRNA news agency. Authorities fear more people could be trapped under the debris. The deadly collapse has raised questions about the safety of similar buildings in the country and underscored an ongoing crisis in Iranian construction projects. The collapse reminded many of the 2017 fire and collapse of the Plasco building in Tehran, which killed 26 people. In Tehran, the city’s emergency department warned that 129 high-rise buildings in the capital remained unsafe based on a survey in 2017. The country’s prosecutor general, Mohammad Jafar Montazeri, has promised to address the issue immediately. Abadan has experienced previous disasters. In 1978 an intentionally set fire at Cinema Rex – a few blocks away from the collapsed building in modern Abadan – killed hundreds. Anger over the blaze triggered unrest across Iran’s oil-rich regions and helped lead to the Islamic Revolution that toppled Shah Mohammad Reza Pahlavi. Abadan, in Iran’s oil-rich Khuzestan province, is home to Iran’s Arab minority who have long complained about being treated as second-class citizens. Arab separatists in the region have launched attacks on pipelines and security forces in the past. Videos and the newspaper Hamshahri noted that two tribes had entered the city to support the protests.