The death of a prominent Syrian rebel leader is being seen as a major blow to the tenuous peace process, with the opposition ' s interim leader warning that other commanders could also be targeted for assassinations. Zahran Alloush, the leader of the Jaysh al-Islam group, was killed on Friday in an air strike claimed by Syrian government forces. "They killed a man who was going to play a crucial role in Syria," Ahmad Tumah, the designated opposition prime minister, told Al Jazeera's Hashem Ahelbarra on Saturday. "The death of Zahran could lead to more targeted killings of prominent opposition commanders and politicians." Zahran was considered a credible and charismatic leader who had united various rebel groups. At the time of his death, he reportedly commanded as many as 20,000 "mainstream" Syrian fighters. Al Jazeera's Ahelbarra said that Tumah is concerned that Russia and Syria "are willing to go after every single powerful person in the opposition to undermine the whole [peace] process". Tumah accused the government of President Bashar al-Assad of deflecting attention from "the fight for political right and against tyranny" to a fight against the Islamic State of Iraq and the Levant (ISIL) group, which he said was the main concern of the international community. Tumah said that while he still intends to attend the peace talks in Geneva, Switzerland, in January, Assad should not have any role in the future of Syria.v