Ahrar al-Sham, which is widely described by analysts as an ultra orthodox Salafist group, expressed "deep condolence" in the Arabic statement for Mullah Omar, who Afghanistan said on Wednesday had died more than two years ago.
It said the Taliban leader had "reminded us of new meanings of jihad and devotion," and had taught "how to build the (Islamic) emirate in the hearts of the people before it becomes a reality on the ground".
The statement comes after Ahrar al-Sham wrote opinion pieces last month - one published by the Washington Post and another by Britain's Daily Telegraph - in which it presented itself as a Syrian national force, distancing itself from cross-border jihadist groups.