US criminal investigators are probing whether hackers broke into financial news company Dow Jones and seized market-moving information prior to publication, an FBI spokeswoman said Friday.

"We are aware and we are looking into it," the FBI spokeswoman told AFP, confirming a news report from Bloomberg News reporting the investigation.

Bloomberg, citing unnamed sources, reported that the computer systems of Dow Jones & Co. were infiltrated by Russian hackers, who stole information to trade on before it was published.

Bloomberg said it was not clear if the information stolen included news stories, or embargoed financial data that had not yet been published.

Dow Jones, part of Rupert Murdoch's News Corp, which owns the Wall Street Journal, expressed skepticism about the report from Bloomberg, a head-to-head competitor in financial news and data.

"To the best of our knowledge, we have received no information from the authorities about any such alleged matter, and we are looking into whether there is any truth whatsoever to this report by a competitor news organization," a Dow Jones spokeswoman said.

Dow Jones disclosed last week that hackers had gained unauthorized access to its systems and sent solicitations to current and former subscribers. That hack affected payment data for fewer than 3,500 people, the Wall Street Journal reported.

Bloomberg said the current hack is considered far more serious. The agency said it was not clear if the two incidents were related.

The case comes on the heels of numerous other hacking episodes involving sensitive market information. US prosecutors in August brought charges against a pair of hackers in Ukraine who stole unpublished corporate press releases from online public relations services like Business Wire and sold them to people who traded shares on the information.