At least 20 bystanders were injured in the blast, in a predominantly Christian area of the Lebanese capital near the Metropolitan Hotel, the channel said.
The attack came six days before parliament's vote on a new president, to replace the pro-Syrian Emile Lahoud.
Several cars including two vehicles used by politicians were set on fire by the explosion, which also damaged several buildings. The news channel said it was not yet clear whether there were people in the other vehicles at the time of the blast.
Ghanem, 64, was a member of the Christian Phalange Party, part of Lebanon's ruling pro-western coalition. The killing is the eighth fatal attack on prominent anti-Syrian figures in Lebanon in the last two years. The first was the assassination of former prime minister Rafik Hariri, which sparked the "cedar revolution," a series of protests that led to the withdrawal of Syrian troops from Lebanon and the disbanding of the pro-Damascus government.
