The European Broadcasting Union (EBU) has called on the Greek government to reopen public broadcaster ERT, after it was shut down suddenly on Tuesday.
EBU president Jean-Paul Philippot is to hand over a petition in Athens signed by 51 European directors general, including the BBC's Tony Hall.
The EBU called the government's action "anti-democratic" and "unprofessional."
The Greek government said the closure was an essential measure to help meet the country's debt bailout obligations.
Viewers watching the news on the main TV channel saw the screens go to black late on Tuesday evening.
Journalists however refused to leave the building and online and satellite broadcasts are being maintained with the help of the EBU website.
The Greek government called ERT a "haven of waste" and said they would relaunch it as a smaller, independent public broadcaster.
"ERT is a case of an exceptional lack of transparency and incredible extravagance. This ends now," said government spokesman Simos Kedikoglou.
ERT, which began broadcasting in 1938, is funded by a direct payment of 4.30 Euros (£3.80) 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.
Since its sudden closure, nearly 2,700 workers have lost their jobs, but they will be able to apply to work for the new corporation.
Employees have protested outside the building since Tuesday and it has also sparked a 24-hour general strike in the country.
The Greek government has pledged to cut thousands of public-sector jobs in order to receive billions of euros in rescue loans from the European Union and International Monetary Fund.