Several major firms targeted by international hackers

Danish sea transport company Maersk, British advertising giant WPP and the French industrial group Saint-Gobain all said they came under attack and put protection protocols in place to avoid data loss.

"Most of our IT systems are down acros the s all business units due to a virus. We continue to assess the situation. The safety of our operations are top of our priorities," Concepcion Boo Arias, spokeswoman of Maersk Line, told AFP.

A Saint-Gobain spokesperson told AFP that the company also "is target of a cyberattack. As a security measure we have isolated our computer systems to protect our data".

WPP tweeted that "IT systems in several WPP companies have been affected by a suspected cyber attack. We are taking appropriate measures & will update asap".

The three groups were the first major businesses to be hit by what is believed to be a ransomware attack of the so-called Petya type, which earlier affected Russia and Ukraine.

"This is a bit like a flu epidemic in winter," said Nicolas Duvinage, head of the French military's digital crime unit.

"We will get many of these viral attack waves in coming months," he said.