image captionIn an internal survey, more than two thirds of BBC Persian service staff said they had been harassed

The BBC has complained to the UN about Iran's harassment of staff at the BBC Persian service.

It says Iranian intelligence agents have threatened to kidnap London staff and take them to Iran.

This is not the first time the BBC has taken the rare step of appealing to the UN for their safety.

Iran has previously denied the allegations, and accused BBC Persian of spreading false information to encourage its government's overthrow.

The BBC's legal representatives have urged the UN's Human Rights Council (UNHCR) to take action on the issue.

An estimated 18 million Iranians – almost a quarter of Iran's population – regularly use the BBC's Persian service online, on radio or via satellite television.

But the Farsi language service is banned in Iran, and authorities there have previously detained people for alleged links to the BBC outlet.

In an internal survey of 102 BBC Persian staff, carried out in March 2020, 71 said they had experienced harassment. A third have also had one or both parents harassed or called in for questioning by Iranian authorities, and over half say they feel under pressure to leave their jobs.

On Thursday, the BBC hosted a virtual side event, coinciding with a UNHRC meeting, to raise concern about what it says is an escalating campaign of harassment by Iran towards BBC Persian journalists and other Farsi-language media.

Among those speaking at the event was BBC Persian reporter Kasra Naji, who spoke about the threats and cyberbullying, which he, his colleagues and their families had endured.

image copyrightGetty Imagesimage captionIranian government supporters have previously protested against BBC news coverage

Mr Naji said that, over the 2020 Christmas period, six staff had family members called in for questioning by Iranian intelligence agents. All were allegedly told to pass on death threats to their London-based relatives.

During every interrogation, officials made reference to Ruhollah Zam – a Paris-based opposition journalist who was enticed to travel to Baghdad in 2019, where he was kidnapped and taken to Iran. Mr Zam was executed last year for allegedly fermenting unrest with her writing.

"Perhaps the most shocking thing is the intelligence officers who made these threats against our lives were so comfortable that they handed over their phone numbers for us to contact them – acting with total impunity on behalf of the state," said Mr Naji.

"We ask you to help shine a light on what's happening to us. It's the only way to safeguard us," he added. "It's a matter of life and death for us – and our families – to speak out."

The BBC says Iran began targeting its Persian service after the country's 2009 presidential elections, when millions of Iranian took to the streets claiming their votes had been stolen.

Allegations of fraud led to months of unrest, with Iran authorities blamed on western governments and international media – including the BBC.

Since then, the BBC says staff have been subjected to an campaign of harassment and death threats, which has escalated in recent years, warranting UK police protection in a number of cases.

In one instance, a reporter received threats to her life via Skype, and was told to quit – or to spy on her colleagues – in return for the freedom of her 27-year-old sister, who had been arrested in Iran.

Back in 2017, Iran's judiciary also issued a freeze on all assets of BBC Persian staff. Then in 2018, Iran accused 152 current and former staff and contributors of "conspiracy against national security", and initiated criminal investigations.

That year, the BBC made its first complaint to the UN, and in March 2019 a group of UN experts condemned Iran's treatment of the broadcaster, saying that its actions violated international law and "ultimately [constituted] serious threats to global security".