A power generation plant in Britain was left out of operation for four days due to a cyberattack by hackers reportedly linked to Iran, the Telegraph reported on Sunday.

The incident, according to the exclusive report, took place during July.

At the same time, cyberattacks were under way against water management infrastructure in the US, about which the White House also expressed concern.

This is the first time Iranian hackers have managed to knock out a power generation plant, and for such a long period, given that such plants are normally classified among critical infrastructure.

The British newspaper does not name the facility, but sources maintain it is a small-scale plant, and that its being out of operation did not affect the grid.

British and American intelligence agencies have repeatedly warned of the danger posed by hackers from Russia, China, Iran and North Korea, who bombard critical national infrastructure and government bodies with attacks on a daily basis.

In the past, disruptions have hit NHS systems, schools and commercial industrial facilities, including Jaguar Land Rover’s production lines.

Foreign hacking groups have also stolen customer data from retail businesses, as well as voter registers from the UK Electoral Commission.

However, no hacker appears ever to have succeeded in paralysing the operation of a British power station, despite warnings that attacks on national infrastructure are a frequent occurrence.