Zahran Alloush, head of the Jaish al-Islam (Islam Army) Syrian rebel group, speaks during the wedding of a fighter in the group on July 21, 2015.

The killing of a Syrian rebel chief in an air raid last week does not serve the peace process in the war-ravaged country, Saudi Foreign Minister Adel al-Jubeir said Tuesday.

Zahran Alloush, the head of the Saudi-backed Jaish al-Islam, the foremost rebel group in Damascus province, was killed on Friday in a strike claimed by Syria’s government.

“Attempts to assassinate leaderships fighting Daesh do not serve the peace process and (efforts) to achieve a political solution in Syria,” Jubeir said, using the Arabic acronym for the Islamic State of Iraq and Syria (ISIS) group.

“I don’t know what the Russians have in mind,” he told reporters, in reference to the killing.

The minister was speaking at a joint news conference in Riyadh with his Turkish counterpart Mevlut Cavusoglu.

Jaish al-Islam has fought off both Syrian government forces and ISIS militants in its Eastern Ghouta bastion, east of Damascus.

It even agreed to eventual peace talks with the regime of Bashar al-Assad, during an unprecedented meeting in Riyadh this month of various Syrian opposition groups.

Analysts have warned that Alloush’s killing could also thwart potential peace talks between the regime and the opposition, which the U.N. announced could begin next month.

Saudi Arabia is a key backer of Syrian rebel groups battling Assad’s regime, and Jubeir reiterated previous demands that Assad be removed from power.

Cavusoglu echoed his counterpart’s calls.

“Our views on Syria match. We cannot reach a solution with Assad’s presence,” he said.

Separately, he said the majority of Russia’s air strikes on Syria are not targeting ISIS.

“If you are really willing to confront IS, then let us agree and eliminate it,” he said, addressing Russia which he accused of having “goals other than eliminating ISIS.”

A bitter diplomatic row flared between Moscow and Ankara, which back different sides in Syria’s war, after Turkey shot down a Russian fighter jet on its border with Syria at the end of November.

Russia says its armed forces have conducted 5,240 sorties in Syria since launching its bombing campaign on September 30.

Moscow had accused Turkish President Recep Tayyip Erdogan and his family of involvement in the illegal oil trade with ISIS militants, claims Ankara has strongly denied.

Erdogan arrived on Tuesday in Saudi Arabia, where he held talks with King Salman.

The leaders discussed mutual relations, regional developments, as well as “cooperation in confronting terrorism and radicalism,” said Jubeir.

They also discussed the 34-nation military coalition against “terrorism” announced by the kingdom this month, he said.

Both leaders also spoke of their “willingness” to form a joint strategic coordination council that would supervise cooperation in the fields of security, military, politics, economy, as well as energy and culture, he added.

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