Graffiti on a wall near the bombings read "Daesh," the Arabic acronym for the Islamic State group (IS), although no group has taken official responsibility for the attacks.
Three of the cars were reportedly owned by members of Hamas, while the other two were owned by members of the Islamic Jihad.
Shrapnel from the blasts hit residential houses, shattering windows and injuring two people who were transferred to a local hospital. No deaths were reported.
Hamas officials have opened an investigation on the explosions.
Since last summer's devastating war in Gaza, there have been growing signs of internal unrest between Hamas security forces and other militant groups, with a string of small-scale explosions.
Many of the more recent attacks are believed to be the work of fringe Salafi groups that have made a name for themselves as unafraid to challenge Hamas, seeking to outbid them in the fight against Israel and the defense of Islam. more