A file picture taken June 25, 2014 shows Zahran Alloush, the leader of Jaish al-Islam, who was reportedly killed in east of Damascus (AFP File Photo)
The killing of Syrian rebel chief Zahran Alloush, fiercely opposed to both the regime and the ISIS, has eliminated a key bulwark against the jihadists and could derail UN-brokered peace talks, analysts say.
The head of Jaish al-Islam, the foremost rebel group in Damascus province, was killed on Friday in an air strike claimed by Syria's government.
Jaish al-Islam has fought off both government forces and IS jihadists in its Eastern Ghouta bastion, east of the capital.
It even recently agreed to eventual peace talks with the regime of Bashar al-Assad.
But with Alloush gone, that centralising force has vanished, says Andrew Tabler, analyst at the Washington Institute for Near East Policy.
"He occupied a space between the extremists and the Free Syrian Army, which was important to hold off the spread of IS in the short term and unify the rebels vis-a-vis the regime in the long term," says Tabler.
Without him, Islamist fighters could lean towards further radicalisation and join jihadist groups, Tabler adds.
Despite Alloush's ferocious opposition to ISIS, Syria's regime and its media consistently referred to him and to Jaish al-Islam as "terrorists".
Syria's army command did so again in the statement claiming responsibility for his death.