BEIRUT (REUTERS) - An explosion at a mosque in Syria's Idlib province on Friday killed at least 10 members of the Al-Qaeda-linked Nusra Front, the British-based Observatory monitoring group said.

The blast in the town of Ariha in north-western Syria went off as members of the Nusra Front gathered at the mosque for iftar, the meal with which Muslims break their fast during the holy month of Ramadan.

Observatory, which tracks the war, said the explosion in Salem Mosque in Ariha, also killed a senior non-Syrian member of the hardline militant organisation.

No group announced responsibility for the blast, but supporters of Nusra Front blamed rival ultra hardline Islamic State in Iraq and Syria (ISIS) militants who have fought the group on several front lines in Syria.

A coalition of rebel groups called Jaish al Fateh, or Conquest Army, in which Nusra Front is a major part of its composition, have controlled most of Idlib province since the capture of the provincial capital in March.

The region borders Turkey and neighbours President Bashar al-Assad's heartland in Latakia province on the Mediterranean coast.