Early reports blame Petya, a variant of the infamous WannaCry ransomware

A cyberattack has caused outages on several government websites, and those of companies in several countries, including Ukraine, Russia, Denmark and the UK.

The hack started, or was first discovered in Ukraine, with Ukraine’s interior minister describing it as a variant of the WannaCry ransomware, and calling it the “worst” in Ukraine’s history.

Adviser Anton Gerashchenko said Ukrainian IT systems had been targeted with “Cryptolocker” a version of WannaCry, the virus that locked up more than 200,000 computers in more than 150 countries in May.

British advertising company WPP is also a victim of the cyberattack with reports of ransom demands and systems crashing. Several of WPP’s agencies including GroupM and MediaCom, and Y&R are thought to be affected by the attack.

Mary Heather, senior director at WPP-owned agency Burson-Marsteller, confirmed the attack on Twitter saying the agency had “no access to technology”.

“IT systems in several WPP companies have been affected by a suspected cyberattack. We are taking appropriate measures & will update asap.”

Russian oil producer Rosneft and Danish shipping company Maersk have all reported disruption as a result of a ransomware attack earlier today.

The story is still unfolding and updates will follow.