Greek state TV and radio were dramatically pulled off the air late on Tuesday, hours after the government said it would temporarily close all state-run broadcasts.
The government announced it would lay off about 2,500 ERT workers, around 600 of whom are journalists, as part of a cost-cutting drive demanded by the bailed-out country's international creditors.
Reuters reported that a "slimmed-down" version of the broadcaster would be relaunched in a few weeks, after being unceremoniously pulled off on Tuesday.
The head of ERT's foreign desk, Odin Linardatou, said journalists were "very shocked, we are angry." She told the BBC's Newshour programme: "What I cannot accept in a democracy is that Greece will not have a public broadcaster."
Journalists, trade unionists and politicians gathered for protests outside the building, calling it a 'coup d'etat' by the government to muzzle criticism.
Journalists have announced an indefinite strike at outlets across the country and a newspaper strike will begin Thursday.
Index on Censorship's Chief Excecutive Kirsty Hughes told HuffPost UK: “The sudden closure of Greek public broadcaster ERT by the governement shows an attitude to media freedom that is extremely troubling.
"Throughout the Greek economic crisis the authorities have been eager to shoot the messengers, whether they be ERT employees or Kostas Vaxevanis, publisher of the ‘Lagarde list’. Narrowing the discussion through underming free media will not solve Greece’s problems.”
Staff at the channel have also been continuing broadcasts on the internet, according to Reuters.
Government spokesman Simos Kedikoglou told Reuters the shutdown was decided six weeks ago.
"We didn't shut down ERT, we temporarily suspended its operations to fix it and make it work on a healthy basis," he said.
Opposition leader Alexis Tsipras will meet State President Karolos Papoulias on Wednesday to protest against the decision.
On Tuesday, he called the closure "a coup, not only against ERT workers but against the Greek people.
“Many times the word ‘coup’ is used as an exaggeration,” he said. “In this case, it is not an exaggeration.”