Globovision is facing several investigations that could take it off air
A group of some 35 people identified as radical supporters of Venezuelan President Hugo Chavez have attacked an opposition TV channel, Globovision.
Images broadcast by the station showed the group forcing their way into the compound and firing tear gas.
Officials condemned the attack which comes as the government adopts a series of measures regarding the media.
Thirty-four radio stations have been closed for "irregularities". Critics say it is an assault on free speech.
Globovision, which has been highly critical of President Chavez, is facing several investigations that could also take it off air.
On Monday a group of activists from the Union Patriotica Venezolana (UPV), which supports Mr Chavez, rode on motorcycles into Globovision's headquarters and fired tear gas.
Images broadcast by the station showed a woman identified as Lina Ron, a UPV leader and street activist, taking part.
Globovision's Director General Alberto Federico Ravell condemned the attack and urged Mr Chavez to rein in his supporters.
Interior Minister Tareck El Aissami said the violence was "criminal" and promised an investigation.
The incident comes as the arguments over control of the media in Venezuela become increasingly bitter.
Thirty-four radio stations were ordered off air after the government said they were in breach of the rules for registering or had allowed their broadcast licences to expire.
Some 200 other stations are under investigation.
The government says it is trying to make the media more democratic.
"The state is retaking control of concessions that were being used in an illegal way over more than 30 and 40 years," said Public Works Minister Diosdado Cabello, who is the head of the telecommunications agency.
"It's an act of justice."
But critics say the move is aimed at giving more space to media that support Mr Chavez and is an attempt to muzzle any critical voices.
Venezuela's National Assembly is due on Tuesday to begin discussing legislation under which journalists could be imprisoned for up to four years for broadcasting or publishing material that attacks "the peace, security, and independence of the nation and the institutions of the state".
Venezuela still has many private radio stations and newspapers that are stridently opposed to the president but in recent years the government has built up its network of state-run media.