The vehicle exploded in the border town of Ras al Ain, which was taken by the Syrian rebels in 2019 from the Kurdish-led YPG militia. Two of those killed were children, residents said, Reuters reported.
It was not immediately clear who was behind the blast.
Images from the scene taken by residents showed a group of people standing around the burning and mangled wreck of the vehicle.
Video footage showed people carrying what appeared to be at least one dead person in a blanket.