Venezuelan opposition groups have protested against a decision to take 34 radio stations off the air, calling it an attack on freedom of speech.
As the stations stopped broadcasting on Saturday, staff said the move was aimed at giving more space to media that support President Hugo Chavez.
More than 200 other radio stations are expected to close in coming weeks.
The government says the stations are in breach of the rules for failing to hand in their registration papers on time.
The move to close the stations comes as the arguments over control of the media in Venezuela are becoming increasingly bitter, the BBC's Will Grant reports from the Venezuelan capital Caracas.
This week a tough new media law was proposed under which journalists could be imprisoned for publishing "harmful" material.
The opposition mayor of Caracas, Antonio Ledezma, said the closure of the stations showed the government was "scared of freedom of expression".
Opposition politician Juan Carlos Caldera said the government had "turned into a mutilator of rights".
But Diosdado Cabello, head of the national regulator and public works minister, said there was no evidence that the closures were against the law, adding that they were part of efforts to make the media more democratic.
"When we - the national government, the revolutionary government - took the decision to democratise the radio-electrical spectrum... we were speaking seriously," he said.
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