Islamic State group jihadists have killed a senior commander in Iran's Revolutionary Guards in Syria, the elite branch of the Iranian military said Friday.

General Hossein Hamedani was killed on Thursday by IS "during an advisory mission" in the northern region of Aleppo, a Guards statement said.

Russian airstrikes in northern Syria have destroyed the arms depots of a U.S.-backed rebel faction and wounded several of its fighters, the group told AFP on Wednesday.

"At 5:30 pm (1430 GMT) on Tuesday, our bases in the western parts of Aleppo province were targeted by Russian airplanes... which completely destroyed our warehouses," said Mustafa Halabi, a spokesman from the Suqur al-Jabal group.

The Russian air campaign in Syria has thrown an immense obstacle in the way of President Recep Tayyip Erdogan's vision for the future of the country, enraging the Turkish leader and leaving Ankara increasingly sidelined.

Russia's air strikes are aimed at propping up the regime of President Bashar Assad, the very ruler who Turkey has for years insisted must be ousted if there is to be any solution to the Syrian crisis.

Russia's defense ministry on Tuesday dismissed as "absolute lies" claims that its jets had bombed the Syrian city of Palmyra after Syrian state TV reported the strikes.

"All reports by foreign media that Russian planes have allegedly conducted air strikes against the city of Palmyra are absolute lies," ministry spokesman Igor Konashenkov said, Russian news wires reported.

NATO Secretary General Jens Stoltenberg said Tuesday that Russian violations of Turkish airspace were "not an accident" after Turkey complained of two incursions by Moscow's jets.

"For us, this does not look like an accident, it is a serious violation," Stoltenberg told reporters at NATO headquarters in Brussels ahead of a meeting of the alliance's defense ministers later this week.

Divided over the fate of President Bashar Assad, Arab countries have kept silent over Russian air strikes in Syria, apart from Cairo which openly supports Moscow's campaign, experts said.

"The Arab world has lacked regional leadership for years from within the region, and in that void, the U.S. and Russia have been engaging," said H.A. Hellyer, Middle East policy expert at the Washington-based Brookings Center.

U.S. Defense Secretary Ashton Carter said Monday that Russia is pursuing a "losing strategy" in Syria and that it must live up to its commitments in Ukraine.

Speaking in Madrid at the start of a five-day trip to Europe, Carter told Spanish military officials that by carrying out bombing in Syria, Russia had only worsened the four-year conflict.

Turkish President Recep Tayyip Erdogan on Saturday urged Russian counterpart Vladimir Putin to reconsider Moscow's bombing campaign in Syria, accusing the Russian military of turning a blind eye to the killing of dozens of civilians.

Speaking in an interview with Al-Jazeera Arabic, Erdogan expressed anger that whereas Moscow had informed Ankara it would be attacking Islamic State (IS) jihadists in Syria, it had in fact targeted moderate Syrian rebels.

The new band of rebel recruits was supposed to prove the United States could train moderate Syrian fighters to defeat the jihadists in the war-ravaged nation.

But soon after returning to Syria, the American-backed fighters handed over a quarter of their ammunition and other equipment to a local Al-Qaida affiliate, known as the Al-Nusra Front.

Social Affairs Minister Rashid Derbas stressed the importance of a functioning cabinet that would be able to tackle the international aid presented to Lebanon in its efforts to support Syrian refugees, reported al-Joumhouria newspaper on Friday.

He told the daily: “The international backing that Lebanon received from the International Support Group in New York should be translated into tangible aid.”