The World Bank's computer network has been raided by hackers on numerous occasions over the last year, putting financial data at risk, according to a report by US network Fox News.
Fox - which has obtained internal World Bank e-mails and memos - says servers in the organisation's treasury unit were "deeply penetrated with spyware last April".
The first breach was discovered last September by the FBI during a separate investigation.
There have been at least six major intrusions over the last 12 months - the most recent in September - says Fox. Two of the intrusions came from the same group of IP addresses in China.
An internal memo obtained by Fox says at least 18 servers have been compromised, five of which contained "sensitive" data. These include a security and password server and a human resources machine holding images of staff documents.
According to Fox, an internal investigation found that spyware was covertly installed on workstations inside the bank's Washington headquarters - allegedly by one or more contractors from Indian IT vendor Satyam Computer Services.
Fox says that since the breach, a multi-million dollar IT services contract with Satyam has not been renewed.
After Fox published its story, the World Bank sent a statement admitting it was the subject of hacking attempts but insisting that no attack had accessed sensitive data.
The bank says the story is "wrong and is riddled with falsehoods and errors". Fox says it stands by its report.
World Bank Under Cyber Siege in 'Unprecedented Crisis' - Fox News