Image copyright Getty Images

Investigations are under way after at least three Zoom meetings were infiltrated by people sharing footage of children being sexually abused.

The latest incident occurred on Tuesday during a legal education seminar on the video conferencing platform.

A law lecturer, who was a guest speaker at the online event, said his computer screen was "overtaken" by "incredibly distressing" footage.

Zoom said it was "looking into" what had happened.

The case has been referred to the Child Exploitation and Online Protection Centre, which is part of the National Crime Agency (NCA).

James Lee, reader in English law at King's College London, told BBC News around 40 people were logged into the meeting, which had been publicised on social media.

About 20 minutes in, as he delivered his presentation, the session was interrupted.

"All the screens were overtaken by someone sharing abuse images," said Mr Lee.

"I tried to pull all the plugs out of my computer.

"I've never seen anything like it - it was incredibly distressing."

'Absolutely sickened'

The event was suspended but when it resumed more child abuse footage appeared, so it was abandoned.

It is thought three pre-recorded video clips had been played. They were described by those present as containing images of the most extreme abuse of very young children.

Prof Michael Doherty, from Lancaster University, who organised the virtual meeting, said on Twitter: "Just had an absolutely awful experience of Zoombombing... huge apologies to everyone in the meeting.

"We will need to move to a different system with passwords and invitation. Absolutely sickened," he wrote.

Last week, a Zoom meeting organised by the 40,000-strong Federation of Young European Greens was infiltrated by someone streaming child sexual abuse material.

It was reported to police in Belgium, where the organisation is based.

A similar incident is also believed to have happened last Friday during an online discussion about Covid-19 contact tracing apps, hosted by the Open Rights Group, which aims to "preserve and promote" people's rights in the digital age.

The Internet Watch Foundation, which works to remove child abuse content from the web, said it had been alerted.

Zoom said it was "looking into" what had happened.

A company spokesperson said: "These incidents are truly devastating and appalling, and our user policies explicitly prohibit any obscene, indecent, illegal or violent activity or content on the platform.

"Zoom strongly condemns such behaviour and recently updated several features to help our users more easily protect their meetings."

The firm said it had made the Zoom Meeting ID less visible and had added a new security icon to its meeting controls.

"We encourage users to report any incidents of this kind either to Zoom so we can take appropriate action or directly to law enforcement authorities," the spokesperson added.

Earlier this month, Zoom's chief executive, Eric Yuan, apologised for "falling short" on security issues and promised to enhance safety and privacy features.

The NCA said it was aware of a "number" of reports.

NCA deputy director Charles Yates said: "The NCA is working with partners in the UK and abroad, law enforcement and private sector, to respond to these cases.

"Operators of these platforms need to do all they can to ensure their services aren't exploited or compromised in this way, particularly at a time when live streaming applications have reported significant increases in their use."