The Wall Street Journal reported on Tuesday that the FBI is investigating a computer-security breach targeting Citigroup Inc. The newspaper reported that tens of millions of dollars was stolen by computer hackers.

But a short time later, Citigroup denied the report. The financial company sent employees in U.S. a memo on bank branches to help them respond to questions. WSJ did not back down from its story, and neither did Citigroup.

The newspaper said the attack targeted Citigroup's subsidiary that includes its North American retail bank and other businesses. It was unclear whether the thieves gained access to Citibank's systems directly or through third parties. The newspaper also reported that the computer hackers appeared linked to a Russian cyber gang.

Joe Petro, managing director of Citigroup's Security and Investigative services, said, "We had no breach of the system and there were no losses, no customer losses, no bank losses." He added later: "Any allegation that the FBI is working a case at Citigroup involving tens of millions of losses is just not true."

For more on this hack attack:
- see this Wall Street Journal article

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