Authorities say the man runs a car sales business and that they are investigating the possibility of personal rivalry as a motive for the attacks.

Greek local media reported that the victim had been targeted in the past, with his car allegedly booby-trapped in 2004.

Attacks over business differences, including bombings and assassination attempts, are not unusual in Greece.

In other news of violence, Greek riot police clashed with stone-throwing protesters on Thursday during a march against a grenade attack on the offices of a leftist rights group.

Officers fired tear gas at a group of youths who broke out of the demonstrators and threw stones and a petrol bomb at police.

No injuries or arrests were reported.