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."
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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.
'Clear victory for terrorism'
In a separate statement, the National Coalition for Syrian Revolutionary and Opposition Forces, an umbrella organisation headed by Tumah, condemned Zahran's killing, describing it as "a clear victory for terrorism and ISIL".
"It weakens the free army factions that confronted terrorism and undermined its foundations," the statement said on Saturday.
"The attack is also an attempt to abort the UN efforts of a political settlement."
Jaysh al-Islam is said to have named Issam al-Buwidani as Alloush's replacement.
Late on Friday, Buwidani called on the armed opposition to close ranks and unify against Assad. He also condemned what he called the "forces of evil" conspiring against the rights of Syrian civilians.
Speaking to Al Jazeera, Rami Khouri, of the American University in Beirut, said "knocking off" Alloush was "a real blow to the mainstream nationalist opposition".
"The Russians and the Syrians, together or one of them, killed Alloush, presumably because they don't want this kind of powerful, credible, leader who is willing to engage diplomatically," Khouri said.
"They don't want that kind of strong centrist Syrian-based opposition group to gain ground. By killing the leader, they think they can knock out the whole group."
Elias Hanna, a retired Lebanese general, said while it remains to be determined who was responsible for carrying out the fatal air strike, it is the Syrian regime and Russia who are the "main beneficiaries" of Alloush's death.
"Killing Zahran Alloush means they don't have any military opponent on the ground," he said.
Source: Al Jazeera