Greek political parties and unions have urged the government to reverse its surprise decision to shut down state broadcaster ERT - with the loss of nearly 2,700 jobs.
The measure is designed to help Greece meet its debt bailout obligations.
Most of the broadcaster's output has been taken off-air, although shortwave radio and internet broadcasts continue.
Prime Minister Antonis Samaras stood by his move, describing ERT as "the symbol of waste and lack of transparency".
In a speech to business leaders on Wednesday night, the conservative premier added: "We are not closing down public radio and television. In fact, it is only now that we are going to get proper public radio and television."
Opposition leader Alexis Tsipras earlier urged President Carolos Papoulias to cancel an executive order closing ERT.
Protest rallies are being held in support of the broadcaster's staff, with thousands rallying outside ERT's headquarters in the capital Athens, and unions have called a general strike.
Journalists' unions have called a 24-hour strike across Greece's broadcasters - except for those ERT stations airing rogue broadcasts maintained by workers who have refused to leave their posts.
Mr Tsipras described the closure as "illegal", adding: "Many times the word 'coup' is used as an exaggeration. In this case, it is not an exaggeration."
The decision to close down ERT has also put strain on the country's governing coalition.
"We absolutely disagree with the government's particular decisions and management," the socialist Pasok party, a coalition member, said in a statement. "We will not vote in favour of the law validating this legislative act."
The Democratic Left, another coalition partner, said restructuring ERT was necessary but should have taken place without shutting it.
The move has also been condemned by the head of the Orthodox Church of Greece, Archbishop Ieronymos, who said the state broadcaster had been "violently" closed and that its employees were being "sacrificed" to pay for decades of wasteful administration.
The Geneva-based European Broadcasting Union expressed "profound dismay" at the closure in a letter to Mr Samaras, calling on him to reverse the decision.
The head of ERT's foreign desk, Odin Linardatou, said the announcement had taken journalists by surprise.
"We are 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."
The government says ERT was a huge drain on public resources, and will reopen at a later date under a new format and with considerably fewer staff.
All 2,655 employees will be compensated and allowed to apply for jobs at the revamped organisation.
"ERT is a case of an exceptional lack of transparency and incredible extravagance. This ends now," government spokesman Simos Kedikoglou told a news conference.
The announcement came after months of strikes by ERT employees in opposition to plans to restructure the broadcaster.
Athens has pledged to cut thousands of public-sector jobs as part of agreements under which it receives billions of euros in rescue loans from the European Union and International Monetary Fund.
ERT, which began broadcasting in 1938, is funded by a direct payment of 4.30 euros (£3.80; $6) added monthly to electricity bills.
It ran three domestic TV channels, four national radio stations, as well regional radio stations and an external service, Voice of Greece.