The blast, which occurred last night but caused no casualties, comes as political tensions mount in the Palestinian territory.
"Police have opened an investigation after a makeshift bomb blew up the car of Sheikh Sami Hams in Nuseirat refugee camp" south of Gaza City, a security official told AFP on condition of anonymity.
The vehicle had been parked outside and was completely destroyed, according to witnesses.
It was the latest in a series of unclaimed attacks in Gaza.
Analysts say such attacks indicate the gradual loss of control of Hamas over the enclave since it fought a 50-day war with Israel last year, since when radicals have become increasingly active.