At least one car bomb struck the SDF-controlled city of Raqqa with local Kurdish and Arab media outlets saying there were a number of casualties, including several dead.
Kurdish news portals said a mine exploded, followed by two car bombs that left several dead, including women and children. Other local Arab portals said at least four died in the explosion.
There has been a steady increase in attacks on areas controlled by the US backed Syrian Democratic Forces that are mainly east of the Euphrates River.
The US-backed group led by the Kurdish YPG militia has warned that Islamic State militants would intensify an insurgency after their territorial defeat in their last enclave in Syria.