A dent reported on the bullet-proof rear window of Turkey's pro-Kurdish party leader's vehicle has caused fears that the politician may have been targeted for assassination.

Selahattin Demirtas' bodyguards noticed the dent on Sunday and informed police. The party said it was a failed assassination attempt.

However, the regional governor's office said on Monday that no residual evidence of a firearm was found on the window and ruled out an attack on Demirtas or his vehicle. The investigation was continuing.

Demirtas' People's Democratic Party is on edge after supporters were targeted in deadly attacks blamed on a local Islamic State cell in July and October. Party officials have said Demirtas has received death threats.

Demirtas tweeted in Kurdish: "Death is God's command."