Greek Prime Minister Antonis Samaras faced a political revolt from his ruling coalition partners after the government abruptly switched the state broadcaster off the air.
Screens went black on state broadcaster ERT, cutting newscasters off mid-sentence only hours after the decision was announced.
The Greek government said it was a temporary measure to staunch a waste of taxpayers' money.
Unions called a 24-hour nationwide general strike in protest, and journalists across all media called an indefinite strike.
Some newspapers were shut and private TV stations broadcast re-runs of soap operas and sitcoms instead of the news.
Mr Samaras's centre-left coalition partners said they were furious at the decision to shut the broadcaster and had not been consulted.
Coalition party leaders were meeting with the suggestion left hovering in the air that they could force Mr Samaras into a confidence vote which could bring him down.
The confrontation brought back a febrile atmosphere of political drama.
The Athens bourse was cut to emerging market status by index provider MSCI, making Greece the first country ever to lose the status of a developed market.
The gesture was not only symbolically embarrassing but could also force fund managers that track indexes to ditch investments.
That followed the derailing of Greece's privatisation programme earlier this week with the announcement that a gas firm could not be sold.
The setbacks have reversed a rise in investor confidence that had prompted Mr Samaras to say the risk of Greece being expelled from the eurozone was over and a "Greekovery" was under way.
Centre-right leader Mr Samaras has ruled in fragile coalition with two centre-left parties since narrowly winning power last year.
Angry at the abrupt fashion that ERT was yanked off air, the junior partners, the Socialist PASOK and the Democratic Left, said they would table a law to reverse the move.
One official from the New Democracy party said Mr Samaras was considering calling a confidence vote over the issue, although a senior government official denied plans to do so.
The 75-year-old Hellenic Broadcasting Corporation ERT has shed viewers since the rise of commercial television and radio, and its three statewide stations had just a 13% combined audience share when it was switched off.
Its 2,600-strong staff include 600 journalists.
Many Greeks cite the broadcaster as an example of inefficiency, overspending and jobs given in return for political favours.
Nevertheless, in a country where nearly two thirds of young people are now unemployed after years of relentless cuts and tax hikes, there is a visceral public belief that the government should not slash jobs. Greeks were stunned by the speed with which the closure was executed.
Athens journalists' union ESIEA said its strike would end only "when the government takes back this coup d'etat which gags information".
Some ERT journalists occupied the broadcaster's building in defiance of government orders.
The journalists continued broadcasting over the Internet, showing sombre newscasters deploring the shutdown and replaying images of thousands gathered outside to protest.
ERT's reporters from as far away as Australia appeared on air to describe the outrage of local Greek communities.
"It is our only link with our homeland," said Odysseas Mandeakis, president of the Greek community in Zambia.
The decision to shut ERT was taken by ministerial decree, meaning it could be implemented without immediate reference to parliament.
The government promised to relaunch ERT within weeks, saying it was taken off air so suddenly only due to fears that workers would damage state equipment.
A senior government official said Athens was under pressure to show visiting EU and IMF inspectors that it had a plan to fire 2,000 state workers as required under its bailout, and the ERT shutdown was the only option available to meet the target.
The European Commission said it did not seek ERT's closure under the bailout but did not question the decision either.
France's Socialist government voiced outright condemnation, calling it "very worrying and regrettable".
Opposition leader Alexis Tsipras called it "a coup, not only against ERT workers but against the Greek people", and accused Samaras of the "historic responsibility of gagging state TV".
The far-right Golden Dawn party was the only one that openly welcomed the closure, with lawmaker Ilias Panagiotaros tweeting: "ERT, that Socialist-Communist shack, is finally closing."