Iranian journalists in London have experienced death threats, intimidation and online abuse. One broadcaster working for BBC Persian, the Persian language branch of the BBC World Service, which has its headquarters in London, had her car broken into, and her conversations with family members were tapped.

And last month, Pouria Zeraati, a newscaster with Iran International, a Persian-language opposition TV channel that operates from Britain, was stabbed in the leg outside his London apartment.

The three suspected perpetrators of that attack traveled to Heathrow Airport and left the country within hours, according to the Metropolitan Police Service, which is responsible for policing in London.

Specialized counterterrorism officers are still investigating the motive behind the nonfatal stabbing of Mr. Zeraati, and the Met declined to say where the assailants had flown to. But experts say these targeted incidents are part of a frightening pattern of physical attacks, threats, and surveillance that have become a reality for many Iranian journalists working abroad.

And London, home to a number of Persian-language broadcasters, has become a “hot spot” for transnational repression, according to a report published Wednesday by Reporters Without Borders. The report comes against a backdrop of broader concerns about attempts by Iran to kill or kidnap critics in Britain that were outlined by the country’s security service, MI5, in 2022.

“The Iranian government and its proxies are the principal source of threats and harassment, but not the only one,” said Fiona O’Brien, the bureau director in Britain for Reporters Without Borders, who wrote the report.

Complicating the picture, the harassment comes not only from the Iranian state, but also from Iranian opposition groups, political activists and members of the Iranian diaspora, she said. “For journalists on the receiving end of such abuse, it feels like hostility comes from all sides.”

Iran has long characterized journalists abroad as “enemies of the state,” she said, and there was “very clear evidence and no attempt to hide, actually, that Iran is behind a lot of this repression.”

The report, which included interviews with more than two dozen Iranian journalists in London and their employers, found that online attacks against journalists have risen exponentially, and included death threats and threats of sexual violence. Women were disproportionately affected by the online abuse, with some receiving graphic threats of rape. The Iran-based family members of journalists living abroad have also been subjected to threats and intimidation.

Rana Rahimpour, 41, was a prominent anchor for BBC Persian, but stepped away from journalism last year after 15 years, amid a series of threats and intense pressure on her and her family.

The threats against Ms. Rahimpour were long established, she said in an interview with The Times. Her parents had been subjected to a yearlong travel ban in 2013, had had their passports confiscated and were regularly interrogated in Iran.

As part of a complaint filed by BBC Persian to the United Nations in March 2022, Ms. Rahimpour said Iran had targeted her for more than a decade because the authorities “don’t want fair, trusted or impartial news to reach the shores of my homeland.” She and 152 current and former BBC colleagues were sanctioned by Iran in 2017, in an attempt to discourage their work, according to the complaint.

The threats accelerated after the anti-government protests in Iran in 2022 over the death of Mahsa Amini, which Ms. Rahimpour covered extensively for BBC Persian as its lead anchor.

Her car was broken into in London, and she believes that a listening device was placed inside. Her wiretapped phone conversations with family members in Iran were edited, skewed and broadcast on state-run Iranian outlets in November 2022, recast to make it seem as though she supported the government, she said.

Opposition critics, including Iran International, seized upon the edited recordings and accused BBC Persian of collaborating with the Iranian government. Abuse began to pour in from anti-government protesters as well.

“That was what really, really broke me,” Ms. Rahimpour said. “I thought, ‘You know what, enough is enough. I’ve paid enough to do this job, because I felt I had to do it. But now, I don’t have to do it anymore.’”

Ms. Rahimpour described feeling terribly alone amid the abuse and threats.

“The isolation that comes with this kind of pressure is really staggering,” said Ms. O’Brien of Reporters Without Borders, noting that a number of journalists interviewed for her report had expressed similar feelings.

Transnational repression of this type often increases when Iran’s domestic situation becomes more fraught, and “the perceived threat of journalism rises,” she said.

The report published on Wednesday is just the latest evidence that points to the targeting of Iranian journalists abroad. The BBC World Service issued an urgent appeal this week to a U.N. body, requesting action as its journalists have continued to suffer “comprehensive targeting and intimidation,” its lawyers said in a statement.

And earlier this year, a United Nations fact-finding mission on Iran found that “state authorities harassed, threatened and intimidated journalists and other media employees working outside the country, including those working at the BBC Persian service, Iran International television, Voice of America, IranWire and Deutsche Welle.”

In some cases, the Iranian authorities had arrested, detained or charged the family members of those journalists and broadcasters “in an apparent effort to exert pressure on them and prevent them from reporting on the country,” that report said.

In 2022, two British-based journalists working for Iran International were informed by the Met of threats to their lives, prompting an official warning from Britain’s foreign ministry to Iran’s most senior diplomat in London. Britain and the United States sanctioned a number of Iranian officials who are members of the Islamic Revolutionary Guard Corps earlier this year, for what they said were links to the plot against journalists.

For a time Iran International stopped broadcasting from London because of threats to its staff. Iran International, which is banned in Iran, is owned by Volant Media UK, a London-based company owned by a Saudi British national. It has been criticized for its links to Saudi Arabia, and the Guardian reported in 2018 that it received substantial funding from a company with links to the Saudi crown prince. Iran International denies that it has Saudi state backing.

The company employs around 200 journalists, who produce material for its website, radio station and a broadcast viewed by millions of people inside Iran, via satellite. The stabbing of Mr. Zeraati, who is one of their anchors, happened on March 29, near his home in Wimbledon. He has recovered from the injury.

The Iranian Embassy in London did not immediately respond to a request for comment on the report. But on March 30, the embassy said in a statement that Iran was not involved in the attack on Mr. Zeraati.

“We deny any connection to this incident,” said Mehdi Hosseini Matin, a diplomat at the embassy in London, calling it “strange.”

Adam Baillie, a spokesman for Iran International, said the channel provides private security for its journalists, but that threats against them have risen in recent years. “It was the most shocking of things to happen,” he said of the attack on Mr. Zeraati. “But I wouldn’t say it was unexpected because we are under constant threat.”