Activists say a top commander in al-Qaeda's Syrian affiliate has been killed in an airstrike.

The Britain-based Syrian Observatory for Human Rights says Abdul Mohsen Abdallah Ibrahim al-Charekh, a Saudi better known as Sanafi al-Nasr, was killed Thursday in an airstrike near the northern Syrian town of Dana.

The Observatory's chief Rami Abdurrahman said Saturday it was not clear if al-Charekh was killed by US or Russian warplanes.

Jihadi activists on social media say he was killed by a US drone strike.

Al-Charekh, the alleged leader of al-Qaeda's operations in Syria, was one of six men that the UN Security Council imposed sanctions on last year.

His death came three months after the US killed top al-Qaeda official Muhsin al-Fadhli. Al-Qaeda's Syrian affiliate is led by Abu Muhammed al-Golani.