The European Central Bank has claimed that 25 eurozone banks have failed a health check according to leaked documents.
Nearly one in five of the 130 banks surveyed failed the stress test, the Wall Street Journal and the Daily Telegraph said.
This comes ahead of the publication of the official results by the ECB tomorrow.
The unprecedented health check of eurozone banks comes before the ECB assumes the role of the region's banking supervisor next month.
The Frankfurt-based institution takes on its new watchdog role on 4 November and it hopes that a "comprehensive assessment", made up of a so-called asset quality reviews and a "stress test", will uncover any potentially nasty surprises beforehand.
Citing a draft memo seen by Bloomberg, the Telegraph report said only 10 of the 25 banks which failed the stress test would be told to raise more cash.
The failing banks were thought to be in Ireland, Italy, Greece and Austria and will have until 10 November to fill in capital shortfalls, the paper reported.
The banks were already given a preliminary indication of their outcome on Thursday.