The death toll could climb as many of those injured were in a serious condition.
According to eyewitnesses, two assailants fired assault rifles at the vehicle before fleeing the scene by car.
The weapons, as well as an unexploded grenade, were found at the scene, which has been cordoned off by police. A search for the attackers is underway.
Police said militants of the separatist Kurdistan Workers Party (PKK) could be behind the attack, though no extremist group had claimed responsibility.
The PKK, considered a terrorist organization by the EU, the United States and many other countries, has been fighting for an autonomous ethnic Kurd state in southeast Turkey for nearly 25 years. The conflict has claimed over 40,000 lives.
