PARIS (AFP) - France's financial markets watchdog on Monday (Dec 16) hit Bloomberg with a five million euro (S$7.6 million) fine for a report based on a fake news release that triggered a plunge in the shares of French construction giant Vinci and wiped billions off its market value.

Vinci's shares tumbled by nearly a fifth on November 22, 2016, after several media issued reports based on what purported to be a press release from Vinci.

The statement said Vinci had sacked its chief financial officer and was restating its accounts for 2015 and the first half of 2016 after the discovery of accounting errors amounting to several billion euros.

The financial markets watchdog AMF said Bloomberg distributed "information that it should have known was false".

The AMF said Bloomberg did not respect journalistic ethics "as no verification of the information was undertaken before publication."

The fake statement was almost indistinguishable from a normal press release from the group but was posted on a so-called mirror site. The address of the website was not the normal one and the mobile phone number for the spokesman was incorrect.

The false statement linking to the wrong phone number had even been ostensibly signed by the head of Vinci's media relations department.

Half an hour after sending the original fake statement, the hoaxers sent a fake denial, adding to the confusion, before Vinci issued a genuine denial.

Vinci's shares fell 19 per cent at one point, wiping six billion euros off the company's value.

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Bloomberg News said it was disappointed with the AMF's decision and that it plans to appeal.

"Bloomberg News was one of the victims of a sophisticated hoax... We regret that the AMF did not find and punish the perpetrator of the hoax, and chose instead to penalise a media outlet that was doing its very best to report on what appeared to be newsworthy information," said a spokesman.

AFP was among media that received the fake information but noticed the document had been put online by the mirror site using the address vinci.group rather than vinci.com.