A booby-trapped motorbike exploded in the northeastern Syrian city of Qamishli on Monday, wounding at least four people, Syrian state television reported.
The Syrian Observatory for Human Rights also said a motorbike had exploded but did not immediately report any casualties.
Qamishli is in an area mostly under the control of Kurdish security forces. Bomb blasts, often claimed by Islamic State, have occurred in parts of Kurdish-controlled northeastern Syria but have been rare in the last year.
The Kurdish YPG militia is spearheading a US-backed offensive to drive Islamic State out of the jihadist group's remaining strongholds in eastern Syria, including its former de facto Syrian capital Raqqa.
Islamic State also reported the bombing via its online Amaq news agency, saying it had targeted a vehicle belonging to Kurdish security forces. It did not explicitly claim the attack.