A cyber attack shut down a small power facility in the UK last month following warnings about a pattern of disruptive activity by state and non-state actors. Hackers affiliated to the Iranian regime were behind the attack - which lasted four days, the Telegraph reported.

The newspaper added that the incident coincided with a series of attacks on US water infrastructure in July. The UK government said that a "small-scale energy generator" was affected and that the wider energy system had not been put at risk, but did not disclose which site was affected.

The Department for Energy Security and Net Zero briefed energy chiefs and wrote to companies with advice in response to the attack. A government spokesperson said: "The UK has a highly resilient energy system. We work closely with the energy sector to protect infrastructure and ensure the highest security standards.

"This story refers to an incident impacting a small-scale energy generator, and at no point was there a risk to the wider energy system." The incident was reported to the National Cyber Security Centre (NCSC), an arm of GCHQ, The Telegraph reported.

It is understood that the NCSC did not receive any reports of outages in relation to the cyberattack. The centre has previously warned about a pattern of disruptive cyber activity targeting UK organisations by state and non-state actors. NCSC chief Richard Horne warned earlier this year that hostile states including Iran were increasingly targeting the UK's infrastructure with online attacks.

Liberal Democrats foreign affairs spokesperson Calum Miller said: "Reports that Iran-linked hackers shut down a UK power plant show the threat posed by hostile foreign powers to our national security. "The Government must urgently strengthen plans to secure our energy infrastructure and protect us from attack.