The monitoring systems at the Chernobyl nuclear power plant have been broken by a worldwide hack.

Systems usually used to monitor the area around the power station – which is still an active and dangerous area following the disaster in 1986 – are not working because of the cyber attack, Ukrainian authorities said. Those areas must now be monitored manually, according to a statement.

The entire country of Ukraine is being hit by a sustained cyber attack that has hit some of its most important state and private infrastructure. Though the attack began in the country – and most of the damage is still being done there – it is rapidly spreading across the world, hitting firms across Europe and America.

The hack also took down the power plant's website, which usually hosts information about the incident and the area.

All systems at the plant are continuing to operate normally, authorities warned, and automated monitoring in some areas is still working fine. But monitoring in the industrial zone around the plant is being performed manually, using older technology, the statement read.

Authorities suggested that the problems were a result of that monitoring system running on Windows. That operating system is also thought to be the software hit by the attack, which is a variant of the Wannacry ransomware that took down computers across the world – including the NHS – in May.