AMMAN (Reuters) - Two car bombings in two areas of northwest Syria killed at least six people on Thursday in the latest such attacks in towns held by Turkey-backed rebel groups, witnesses and rebels.

In the northwestern city of Afrin, a 10-year-old girl and a man were killed and at least 20 people were wounded when a car bomb was detonated remotely in a main street only hours after a parade by Turkish-backed security police cadets, a witness said.

Since the Syrian Kurdish YPG militia backed by Washington was driven out of Afrin by Turkey-backed Arab rebels last year, the area has seen frequent bombings blamed by rebels on the Kurdish militia.

The YPG has vowed it will not allow the Arab rebels to consolidate their control over the mainly Kurdish city.

Turkey-backed Arab rebels have said their goal is to allow tens of thousands of their kin displaced by Kurdish-led forces backed by Washington to return to their towns and villages.

Ankara considers the YPG an extension of the outlawed Kurdistan Workers Party (PKK) that has waged an insurgency on Turkish soil since 1984.

Further east, near the city of Jarablus, along the same border stretch with Turkey, at least four members of a Turkey-backed Arab rebel group were killed while trying to dismantle a car bomb in the village of Ghandura, two sources from the area said.

Separately at least 10 people were killed and a number were wounded on Thursday when a bomb blast hit a minibus carrying workers employed in a major oil installation in eastern Syria run by the U.S.-backed Syrian Democratic Forces (SDF) led by the YPG, residents of the area said.