Chernobyl nuclear power plant has been suspended after being hit by ransomware cyber attack, which has been causing chaos across Europe. Some computers at the power plant have been infected by the virus, which has also disrupted the Ukrainian power grid and government offices. A computer team have been working to keep the situation in Chernobyl under control. The virus is a version of the Petya ransomware and staff at the power plant are unable to access reports and metrics on their computers. Ukraine's prime minister said the cyber attack is "unprecedented" but "vital systems haven't been affected".Senior security researcher at Lastline, Marco Cova, said: "The Petya attack looks very similar in its dynamics and techniques to the WannaCry ransomware that caused large disruption just a few weeks ago. "In particular, like WannaCry, it seems to rely on the EternalBlue exploit to automatically spread from one machine to another." Mr Cova said there will be questions as to how organisations could continue to fall for this attack. He said: "This attack also shows that criminal groups are always ready to copy and improve on one another's techniques once they see that something is effective." WPP, the world's biggest advertising business, said a number of its companies had been affected and it was currently "assessing the situation". In a statement, the FTSE 100 firm said: "IT systems in several WPP companies have been affected by a suspected cyber attack. "We are assessing the situation, taking appropriate measures and will update as soon as possible." The National Cyber Security Centre, which is part of intelligence agency GCHQ, said there was a "global ransomware incident". A spokesman said: "We are aware of a global ransomware incident and are monitoring the situation closely. "The NCSC website provides advice to the public and business on how to protect your digital systems." The Chernobyl Nuclear Power Plant is a nuclear power station near the city of Pripyat in Ukraine. It is not known who is behind the attack. Romanian cybersecurity company Bitdefender said: "A massive ransomware campaign is currently unfolding worldwide."