Venezuelan President Hugo Chavez has called the Globovision news channel an enemy of the state just days after closing down another provate station.
Tens of thousands of Venezuelans marched in Caracas in a fourth consecutive day of protests over Mr Chavez's closure of the RCTV network - a move which has sparked international criticism that the leftist leader's reforms are undermining democracy.
State television showed hundreds of government supporters marching in downtown Caracas celebrating the decision.
"Enemies of the homeland, particularly those behind the scenes, I will give you a name: Globovision. Greetings gentlemen of Globovision, you should watch where you are going," Mr Chavez said in a broadcast all channels had to show.
"I recommend you take a tranquilizer and get into gear, because if not, I am going to do what is necessary."
He accused Globovision of trying to incite his assassination and of misreporting protests over the closure of RCTV in a manner that could whip up a situation similar to the coup attempt against him in 2002.
US State Department spokesman Tom Casey called on Venezuelan authorities "to reverse these policies that they are pursuing to limit freedom of expression."
Since coming to power in 1999, Mr Chavez has won the support of the nation's poor majority with a multi-billion dollar social spending program, financed by the nation's oil revenues, that helped him win a landslide re-election last year.
But his critics say his moves to centralise power, politicise key institutions like the military, judiciary and oil industry threaten democracy.
He is forging a single governing party, ruling by decree and considering abolishing limits on how many terms a president can serve.
Given this trend, political analysts had considered the existence of a critical media as the principal safeguard against Mr Chavez following the lead of his communist mentor Cuban leader Fidel Castro.
After RCTV's closure, Globovision is the last main opposition media in the Opec nation, but it does not have nationwide coverage.
Globovision Director General Alberto Ravell said the charges against his channel were "ridiculous" but added he was worried by the government's offensive.
"If this government, with one stroke of the pen, closed the oldest television station in the country [RCTV], that has been on the air for 53 years, how will it not be able to shut this station which is far smaller," he said.
"This is a country with a single party and a single trade union. Now it appears there is going to be a single channel."
Mr Chavez has had a long-running feud with opposition television channels, which openly supported a coup against him in April 2002 and refused to show the massive mobilisation of his supporters that turned the tide back in the president's favour.
CTV's closure on Sunday has led to intermittent clashes between protesters hurling bottles and stones and police firing rubber bullets and tear gas.
The mayor of metropolitan Caracas, Juan Barreto, said up to 187 people had been detained during the protests, mainly students. He said 19 police had been hurt, one surviving a shot to chest thanks to a flak jacket.