Vladimir Putin has dismissed claims that Russian air strikes have killed civilians in Syria, as his government faces criticism from the West that it bombed moderate rebel factions fighting Syria's president instead of Islamic State (IS) fighters.

Russia launched air strikes in war-torn Syria on Wednesday, its first overseas military engagement in nearly four decades, hours after the Russian parliament gave Mr Putin permission to use force abroad.

The head of Syria's main opposition group has accused Moscow of aiming to support Bashar al-Assad's regime and killing 36 civilians in the central province of Homs.

"When it comes to media reports regarding the suffering of the civilian population, we are ready for this information warfare," Mr Putin said.

"Nevertheless, this doesn't mean that we should not heed information like this."

The Russian leader's comments followed those of his foreign minister, Sergei Lavrov, who rejected accusations Moscow bombed moderate rebel factions fighting president Assad.

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Mr Lavrov said the campaign was started "in response to the appeal of the Syrian leadership to help fight ISIL and other terrorist groups," referring to IS.

"The rumours that the target of these air strikes was not IS positions are unfounded," Mr Lavrov told journalists in New York after meeting his US counterpart John Kerry, adding that he has "no data" on civilian casualties.

France and the United States immediately expressed doubts that Moscow was targeting IS fighters.

"Moreover we have also made clear that we would also have grave concerns should Russia strike areas where ISIL and Al Qaeda affiliated targets are not operating," Mr Kerry said.

"Strikes of that kind would question Russia's real intentions in fighting ISIL or protecting the Assad regime."

US Senator John McCain said Russia's initial air strikes targeted recruits in the Free Syrian Army rebel group backed by the US.

"I can absolutely confirm to you that they were strikes against our Free Syrian Army recruits that have been armed and trained by the CIA, because we have communications with people there," Senator McCain, head of the Senate Armed Services Committee, said in an interview on CNN.

Saudi Arabia, a leading foe of the Assad regime, demanded Russia end its raids on Syria, saying the strikes had caused civilian casualties while failing to target the hardline IS militants Moscow says it opposes.

"Countries that have claimed recently to join in the fight against ISIS terrorism, they can't do that at the same time as they support the terrorism of the Syrian regime and its terrorist foreign allies like Hezbollah and the Quds Force and other terrorist sectarian groups," Saudi ambassador to the UN, Abdallah Al-Mouallimi, said.

Australian fighter jets carried out their first strikes against IS targets in Syria earlier this month.

Russia's first air strikes occurred in parts of Syria controlled by rebels, not Islamic State, according to the Institute for the Study of War. ( Institute for the Study of War/Reuters/ABC News )

Russia requests evidence to back accusations

Locals in the opposition-held area of Homs, targeted in Russia's first attacks, said IS had no presence in the region, echoing the assessment of a US official and the Britain-based Syrian Observatory for Human Rights.

The region is of vital strategic importance to the Assad regime's control of western Syria, linking the capital in Damascus to the coastal area including Latakia and Tartous, where Russia operates a naval facility.

Mr Lavrov said the Russian military only went after "terrorist groups" and said that Moscow had requested that American officials back up their accusations with firm evidence.

"They expressed doubt, arguing that there is evidence, which we asked to show us, because we stand by our targets," Russia's top diplomat said.

"Talk began that civilians were hurt by air strikes. We have no such data.

"We carefully make sure that these target strikes are precise."

The defence ministry in Moscow said for its part that Russian fighter jets had carried out 20 sorties and struck "eight Islamic State targets", including a command post in the mountains.

Russia's Kommersant daily on Thursday quoted a military source as saying that the Russian deployment includes Su-24M and Su-34 bombers, Su-30 fighter jets and Mi-24 combat helicopters.

Syrians living in Homs said the jets were flying at higher altitudes than the Syrian air force and emitted no noise to alert the people below to raids.

ABC/wires

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