Hackers attacked the server of the Greek Finance Ministry in protest of austerity and leaked confidential data about the state of the ailing economy, Greek media reported on Monday.

The cyber attack at the General Accounting Office was made "to show solidarity with Greek peoples," said a statement posted briefly on the website signed by the hacker activist group Anonymous, according to reports.

However, Greek police sources who verified the attack, expressed doubts whether the hackers who have claimed responsibility for cyber attacks against state servers worldwide in recent months, have orcherstated Monday's hit.

They suspect that it was local hackers who gained access to confidential documents, including correspondence between Greek state officials and representatives of the European Union and International Monetary Fund lenders who keep Greece afloat since 2010 with loans in exchange of harsh policies.

The extent of the breach has not been fully estimated yet.

The attack came as the parliament is scheduled to vote on a fresh set of austerity measures next week in order to secure further international bailout funding in November to stave off a default which could destabilize the entire eurozone.

Hackers operating under the "Anonymous" group banner have attacked Greek government websites four times since last February.