Tehran has witnessed its largest anti-government demonstrations in decades, as protests swept through dozens of districts across the capital and its wider metropolitan area of nearly 16 million people. For several hours there on Thursday night, security forces appeared unusually restrained. In areas where crowds were especially large, police and security units largely avoided direct confrontation, raising questions about whether the authorities were deliberately holding back. That restraint, however, appears selective and strategic rather than absolute. While Tehran has seen a comparatively cautious approach, reports from smaller cities and provinces around the country tell a far more violent story. According to multiple Iranian human rights organisations, including the Germany-based Kurdish Iranian human rights group Hengaw and US-based Human Rights Activist News Agency (Hrana), more than 40 people have been killed since the protests began nearly two weeks ago. BBC Persian's verification team has confirmed the identities of at least 21 victims through interviews with relatives, many of whom were killed in Lorestan and Kurdish-majority regions of Illam and Kermanshah provinces. Video evidence obtained by the BBC shows security forces firing directly at protesters. At least four security forces have also been killed. Iran's Supreme Leader Ayatollah Khamenei has issued a firm warning, declaring that the Islamic Republic 'will not back down in the face of vandals'. In a speech on Friday addressing the unrest, he framed the protests as foreign-inspired sabotage. Referring to property damage in Tehran, he said demonstrators had destroyed their own buildings 'just to please the president of the United States'. Following the seizure by the US of Venezuelan President Nicolás Maduro, many within Iran's leadership are increasingly concerned that the United States may be serious about its threats, particularly after a 12-day war with Israel last June, during which the US bombed Iran's nuclear sites, and the weakening of Iranian-backed militant groups across the region. It is possible these developments could embolden Washington to strike Iran without fear of significant retaliation. President Donald Trump has loomed large over the regime's calculations. Since almost the start of the protests, Trump has issued repeated warnings to Tehran, stating that the US would respond forcefully if peaceful protesters were killed. In a recent US radio interview, Trump said Iran would 'get hit very hard' if it repeated the mass killings seen during previous uprisings. He downplayed responsibility for deaths so far by attributing some to 'stampedes', but stressed that Iranian authorities had been 'told very strongly' where the red lines lay. It is not clear whether these warnings may be behind the regime's response. In Tehran, where symbolically the costs are greatest, security forces appear to be exercising restraint to avoid images of mass bloodshed. Gunshots were reportedly heard late Thursday night in Tehran, but due to the near blackout of the internet it is difficult to verify exactly what is happening in the city. Outside the capital, however, repression has been swift and lethal. During the mass protests in Iran in 2022 following the death of the Kurdish woman Mahsa Amini in police custody in Tehran, more than 500 people were killed, human rights groups say. The Islamic Revolutionary Guard Corps (IRGC), along with its affiliated militias and anti-riot police, played a pivotal role in violently suppressing those protests. Historically, the Islamic Republic has relied on a layered security apparatus to suppress mass protests. Alongside riot police, the regime deploys the Basij militia - a volunteer paramilitary force under IRGC control - often operating in plain clothes. In more intense situations, command shifts from police to IRGC commanders, signalling that unrest is being treated as a national security threat rather than a civil disturbance. This escalation typically precedes harsher crackdowns, including mass arrests and lethal force. Iran's President Masoud Pezeshkian has called for tolerance of what he described as 'legitimate protests,' but his authority is limited. Ultimate control over security policy rests with the supreme leader, not the presidency. The current approach suggests the regime is buying time, attempting to exhaust protesters, limit casualties in visible areas, and avoid crossing thresholds that could provoke direct foreign retaliation.