MADRID/VIENNA (Reuters) - Austria's Erste Bank (>> Erste Group Bank AG) rejected a report that it was one of at least 11 banks that had failed the European Central Bank's landmark health check, while other banks named by Spanish newswire Efe did not comment.

Efe said Erste, along with banks from Italy, Belgium, Cyprus, Portugal and Greece, had failed the ECB review based on preliminary data, but gave no details of the size of the capital holes at the banks.

The ECB said it could not comment on individual institutions or on speculation. "Any inferences drawn as to the final outcome of the exercise would be highly speculative until the results are final on 26 October," said a spokesman.

Austria's Erste (>> Erste Group Bank AG) told Reuters it had no reason to believe it will fail the test.

Banks have already had some feedback on the outcome of the tests through 'supervisory dialogues' with the ECB. They get the results on Thursday, ahead of a public announcement on Sunday, a week before the ECB becomes supervisor of the euro zone's banks.

"Out of the supervisory dialogue we have no indication we won't pass," an Erste spokesman said. The bank's shares were down 1.6 percent at 4:45 a.m. EDT.

There was no immediate comments from the other affected banks on the report, which briefly moved the euro and led to European stocks reversing their early gains.

The banking sector index <.SX7E> fell 0.6 percent and most shares in the banks mentioned in the report were under pressure.

The other banks listed by Efe were Italy's Banco Popolare, Monte dei Paschi and Banca Popolare di Milano, Greece's Alpha Bank, Piraeus Bank and Eurobank, Portugal's Millennium BCP and Belgium's Dexia. Efe also said a second, unnamed Austrian bank and a Cypriot bank were set to fail.

All three Italian banks declined to comment, though Banca Popolare di Milano's CEO said last week that the feedback he had got from the ECB in the one-to-one meeting was reassuring. Alpha and Millenium BCP also declined to comment, while the other banks could not immediately be reached.

"It is not causing too much of a stir but it is a dampener," said Beaufort Securities sales trader Basil Petrides.

(Reporting by Sarah White and Eva Taylor in Frankfurt, Sudip Kar-Gupta in London, Blaise Robinson in Paris; additional reporting by Reuters buros; Editing by Julien Toyer and John Stonestreet)