A leader of Nusra Front, Al-Qaeda's Syrian affiliate, was killed by unknown gunmen in the northern Syrian town of Ariha, according to the Syrian Observatory for Human Rights.

Nusra Emir Iyad Adl and administrative Nusra leader Mohamed Abdel Wahab were killed in a drive-by shooting, Sky news reported on Thursday, quoting the London-based observatory.

The assailants managed to fled the scene.

The assassination is the latest in a string of killings targeting leaders of Nusra front and Syria's Ahrar al Sham Islamic rebels.

About 20 leaders of the armed opposition were killed since December 2015 in several parts of Syria.

Source: MENA