In a statement yesterday, the movement reported that the Hamas official, who is a Palestinian refugee residing in Lebanon, was targeted in a auto bomb yesterday afternoon.
The official, who identified Hamdan as a Hamas member, spoke on condition of anonymity because he was not authorized to speak to the media.
Hamas leader Jihad Taha blamed Israel for the attack.
Hamdan was lightly wounded in the attack and nearby buildings incurred material damage. "The incident has Israeli fingerprints", Mounir al-Maqdah, the Fatah official, told Reuters.
According to AFP citing medical sources, a BMW detonated when Hamdan opened a door to the vehicle.
The Red Cross confirmed that there was only one person wounded in the blast and said he had been transported to hospital in a civilian vehicle.
Lebanese news outlets said the blast took place as the Palestinian was getting into his booby-trapped BMW in the area of al-Boustan al-Kabir in Sidon, some 40km south of the Lebanese capital, Beirut.
By longstanding convention, Lebanese authorities do not enter Palestinian camps, where security is instead left to joint Palestinian security forces.