Greece's public TV and radio channels are off the air after a shock decision by the government to shut down the state broadcaster's operations with immediate effect, a move affecting nearly 2700 jobs.

Thousands rushed to the broadcaster's main headquarters in a northern Athens suburb shortly after the announcement on Tuesday to show their support.

"ERT is a case of an exceptional lack of transparency and incredible extravagance. This ends now," government spokesman Simos Kedikoglou said at a news conference.

His announcement comes after months of work stoppages by ERT employees in opposition to plans to restructure the broadcaster as demanded by debt-laden Greece's troika of international creditors.

Nearly 500 people also gathered outside the organisation's Thessaloniki branch in northern Greece as news editors union Poesy called on private broadcasters to hold an immediate work stoppage in solidarity.

Kedikoglou said the organisation will reopen at a later stage under a new format and with considerably fewer employees.

As screens around the country went black, the corridors of the broadcaster's headquarters were filled with stunned employees, who seemed at a loss.

"This is a total shock," ERT journalist Pantelis Gonos said.

"We are in contact with a legal adviser and international media organisations."

ERT kept broadcasting as more supporters gathered outside its headquarters, but shortly after 2000 GMT (0600 AEST) transmission was suspended, reportedly in the presence of the police.

According to the state-run Athens News Agency, the gradual process of switching off transmitters around the country started at 1900 GMT (0500 AEST).

"Police went onto the mountain and neutralised our people" who managed the transmitter, said Nikos Roukounakis, who said he has been an engineer at ERT for 30 years.

"This is a coup d'etat," Alexis Tsipras, leader of main opposition party Syriza, who rushed to the ERT premises, told reporters.

As transmission was cut, the finance ministry released a statement saying the broadcaster as an entity had been abolished.

"ERT belongs to the Greek people... It is the only independent, public voice and it has to remain public... We condemn the government's sudden decision," public sector union GSEE said in a statement.

The government said all 2655 employees will be compensated and will be allowed to reapply for a job at a revamped organisation.

The junior partners of Greece's three-party, conservative-led coalition government also expressed opposition to the shock closure.

"We absolutely disagree with the government's particular decisions and management," said socialists Pasok.

"We will not vote in favour of the law validating this legislative act," the party added, noting nonetheless that governmental cohesion was not at stake.

Dimitris Papadimitriou, general director of the radio department and a well-known Greek composer, said that even the 1967-1974 military junta hadn't taken such action.

"Such a thing never happened before, not even during the dictatorship," he complained

On Monday, representatives of Greece's European Union, International Monetary Fund and European Central Bank creditors began a regular audit of the country's progress in implementing its austerity program and structural reforms.

The reforms demanded of Greece include a drastic reduction of the public sector and the merging or closing of public organisations.

The European Broadcasting Union (EBU) urged the cash-strapped country to backtrack on the closure, saying it was a major blow to media independence.

Can't these greco-freakos just shut down th country already, or are countries to big to fail