A ransomware attack hit computers across the world on Tuesday, taking out servers at Russia’s biggest oil company, disrupting operations at Ukrainian banks, and shutting down computers at multinational shipping and advertising firms.

Russia’s Rosneft, one of the world’s biggest crude producers by volume, said its systems had suffered “serious consequences” from the attack. It said it avoided any impact on oil production by switching to backup systems.

The Russian central bank said there were isolated cases of lenders’ IT systems being infected by the cyber attack. One consumer lender, Home Credit, had to suspend client operations.

Cyber security experts said those behind the attack appeared to have exploited the same type of hacking tool used in the WannaCry ransomware attack that infected hundreds of thousands of computers in May before a British researcher created a kill-switch.

Experts said the latest ransomware attacks unfolding worldwide, dubbed GoldenEye, were a variant of an existing ransomware family called Petya.

Russian security software maker Kaspersky Lab, however, said its preliminary findings suggested the virus was not a variant of Petya but a new ransomware not seen before.