Is Lebanon edging towards civil war?Send us your views
Nasrallah hits out at governmentExperts' viewsTimelineIn video:'Declaration of war'
"Gunmen surrounded the building, stormed into the garage and demanded that the army shut down the station," a senior TV official said.
Security sources said Hezbollah and fighters from the allied Amal movement - both Shia groups - had overrun offices of Hariri's Future conglomerate across the predominantly Muslim western half of the Lebanese capital.
The headquarters of the Future media group's Al-Mustaqbal daily was also surrounded by fighters firing rocket-propelled grenades, setting fire to one floor, its managing editor said.
Nadim Munla, the general manager of Future TV, told Al Jazeera that masked armed men entered the control rooms and cut off the cables.
"We have been effectively prevented from broadcasting and doing our jobs as media professionals," he said.
"Hezbollah ... have proven that the gun is stronger than the value of the opinion. We have only one thing left - free speech, and their guns will not silence us."
Lebanese troops evacuated the staff of the TV station's terrestrial and satellite studios in the Kantari area of western Beirut.
Separately, Walid Jumblatt, head of the pro-government Progressive Socialist Party and and leader of Lebanon's Druze community, said in an exclusive interview with Al Jazeera's Rula Amin, that he did not regret his backing for the removal of the head of security of Beirut airport, whom the government accused of being too close to Hezbollah.
"He said that the government should have undertaken these moves earlier, but predicts that the fighting will end soon," Amin said, referring to Jumblatt."I did not anticipate such a strong response from Hezbollah, but ... yes ... the group is much stronger than other armed militias," Jumblatt said.
He also said: "If you want to know what the next move for Hezbollah will be, ask [Mahmoud] Ahmadinejad [the Iranian president]. This situation goes beyond Lebanese borders."Hezbollah control
On the ground, in several neighbourhoods of Beirut, automatic rifle fire could be heard in the worst domestic fighting since the 1975-90 civil war.Hezbollah took control of all roads leading to Beirut's international airport, Lebanon's only air link to the outside world.
Tension between the government and Hezbollah escalated when the cabinet said the group's private phone network was illegal and an attack on the country's sovereignty.
Hezbollah said it was infuriated by government allegations it was spying on Beirut airport and by the cabinet's decision to fire the head of airport security.
The fighting has prompted urgent appeals for calm from the international community.
Saudi Arabia and Egypt called for an urgent meeting of Arab foreign ministers to try to halt the violence.
"An emergency meeting of Arab foreign ministers in Cairo to discuss the crisis will be held in two days," Hossam Zaki, the Egyptian foreign ministery spokesman, said.
The UN Security Council also called for "calm and restraint", urging all sides to return to peaceful dialogue.
Syria, an ally of Lebanon's opposition parties, said the dispute in Lebanon was an "internal affair" and expressed hope the feuding parties would find a solution through dialogue.
Al Jazeera's Mike Hanna, reporting from Jerusalem, said that Shimon Peres, the Israeli president, has called the clashes in Lebanon a "tragedy"."The Israeli government does not view the current situation as a threat, but sees it as an internal matter," Hanna said.
"Israel, however, has always held the position that Hezbollah's intent is to split Lebanon."