PSZAF, in a statement, said Bloomberg had violated a ban on market manipulation.

"Although the news was published due to a technical error, the regulator believes that the news agency failed to apply control mechanisms to prevent false news being published," the statement said.

A London-based member of Bloomberg's communications team, Catrin Thomas, said in an emailed response to questions: "At the moment we're not commenting."

Bloomberg is a competitor of Thomson Reuters in providing news and information.

Bloomberg filed a headline six minutes before the interest rate decision was announced, saying the National Bank of Hungary had lowered its benchmark interest rate from 5 percent to 1 percent.

Bloomberg issued a correction within some 40 seconds, PSZAF said.

Shortly afterwards, the central bank cut its main interest rate by 25 basis points to 4.75 percent.

PSZAF said that it amounted to market manipulation if someone published unfounded, misleading, false information "if the person disseminating the information is aware of the fact that the information is false or misleading, or should have been aware of it had (the person) acted with the care that can be expected in the given situation".

PSZAF said that based on this, Bloomberg had violated the ban on market manipulation.

"The authority regarded as a mitigating circumstance that the publication of the false news was due to an unexpected, automatic technical condition, which it was not possible to avert manually immediately," PSZAF said.

(Reporting by Krisztina Than; Editing by Michael Roddy and Matthew Tostevin)