Political talk show host May Chidiac of the private Lebanese Broadcasting Corporation was inside her car when the bomb exploded on Sunday in Ghadir, a town near the Christian port city of Jounieh, north of the capital, Lebanese security officials and the TV station said.
Chidiac was taken to Hotel Dieu Hospital in Beirut for surgery.
Late on Sunday, the hospital reported that Chidiac's left arm and leg were severed in the blast and her right leg and pelvis were broken.
A hospital statement said she was suffering from various injuries and burns all over her body, adding that her vital organs were "stable" but would need careful monitoring over the next few days.
The attack comes amid rising fears in Lebanon of security deterioration as UN investigation into the assassination former prime minister Rafiq al-Hariri nears conclusion. Two days ago, the UN investigators returned to Lebanon after four days of questioning Syrian officials in Damascus.
The country has been rife with rumors and speculation of more attacks as chief investigator Detlev Mehlis prepares to issue his report in late October.
Prime Minister Fuad Siniora, speaking to reporters outside the hospital in Jounieh, said the bomb, like other recent explosions, was related to the al-Hariri investigation.
Police officers inspect the damaged
car of May Chidiac in Jounieh
"There is no doubt it is all related, we don't want to deny that," Siniora said.
He appealed to Lebanese to be patient.
"We are paying the tax for freedom and independence," Siniora said, adding that he had contacted the US ambassador for technical assistance.
Under the driver's seat
A security official, speaking on condition of anonymity because he was not authorised to speak to the press, said the bomb was made up of less than two pounds of plastic explosives, placed under the driver's seat.
Television footage from the scene showed part of the car's left door was blown off. The front of the vehicle was a twisted wreck.
President Emile Lahoud denounced the attack and, in a statement, called for unity among the Lebanese.
Student unions called for sit-in protests at universities and in downtown Beirut on Monday.
Chidiac, who is in her 40s, is one of several hosts of a daily political talk show at the station, which broadcasts in Lebanon and is widely seen in the Arab world and by Lebanese communities across the world. Chidiac hosted the show Sunday morning with a political analyst from the leading An-Nahar newspaper.
"The country's security is exposed and anyone can fish (in the waters) and place bombs"
Druze politician Walid Jumblatt
LBC, a Christian TV station, is among the most prominent of anti-Syrian media outlets.
The explosion recalls a similar one on 2 June, when anti-Syrian journalist Samir Kassir was killed by a bomb placed under the seat of his car.
Accusations against Syria
Opponents of Syria's role in Lebanon have accused remnants of the Lebanese-Syrian intelligence apparatus of being behind the al-Hariri assassination and other bombings that targeted anti-Syrian personalities and shopping centers and industrial areas since then.
"There are remnants of the security apparatus who seem to be somewhere still causing security breaches. The country's security is exposed and anyone can fish (in the waters) and place bombs," said Druze politician Walid Jumblatt.
In an interview with LBC, Jumblatt called for the appointment of security officials to replace the arrested ones, appointments that have been held up by disputes among political groups within the government.
The UN mission to Syria added pressure on the Damascus government, which has been accused by opponents in Lebanon of involvement in al-Hariri's killing.
Syria denies any role in the assassination, which prompted a wave of anti-Syrian protests here and helped end Syria's almost three-decade domination of Lebanon.