US President Barack Obama warned Friday that Russia's aggressive military campaign in Syria supporting strongman Bashar al-Assad is a "recipe for disaster," though Washington could still work with Moscow on reducing tensions.
Differences between the two have punctuated the last several days of the crisis, in which Russian jets have pounded Syrian opposition forces, but Obama stressed that "we're not going to make Syria into a proxy war between the United States and Russia."
Moscow carried out a third day of air strikes Friday in Syria, saying it targeted Islamic State jihadists, as Russian President Vladimir Putin faced increased international criticism over his military campaign.
The West has raised concerns that Russia is using its campaign against "terrorists" as a pretext to strike at moderate rebel groups opposed to Assad in a bid to bolster its ally.
Putin "doesn't distinguish between ISIL and a moderate Sunni opposition that wants to see Mr Assad go," Obama told reporters.
"From their perspective, they're all terrorists. And that's a recipe for disaster."
The Russian defense ministry and the Kremlin said its planes bombed IS targets six times Friday and also hit the group's jihadist rival, Al-Qaeda's Syrian affiliate Al-Nusra Front.
The US-led coalition urged Russia to stop attacking Syrian opposition forces, warning that it risked escalating the four-year civil war that has already killed up to 250,000 people.
"These military actions constitute a further escalation and will only fuel more extremism and radicalization," seven countries including Turkey, the United States and Saudi Arabia said in a statement.
"We call on the Russian Federation to immediately cease its attacks on the Syrian opposition and civilians."
Russia said earlier it had hit the IS bastion of Raqa for the first time in raids Thursday, destroying a "terrorist training camp" and a command post.
The group is one of many fighting Assad and has seized control of large parts of eastern Syria and northern Iraq.
Some of the rebel groups targeted by Russian jets have been supplied with training and weapons by the United States and its allies.
'Residents very afraid'
"I reminded President Putin that the strikes should be aimed at Daesh and only Daesh," French President Francois Hollande said after talks with his Russian counterpart in Paris, using the Arabic acronym for IS.
The Russian defense ministry said the latest strikes had completely destroyed an IS facility used to produce explosive devices near the city of Maaret al-Numan in Idlib province in northwestern Syria, as well as a nearby base.
They also targeted central Hama province.
But several military sources and the Syrian Observatory for Human Rights monitoring group said Russia had hit areas controlled by groups other than IS.
A security source said they had been aimed at "military positions and command centers held by the Army of Conquest in Jisr al-Shughur... and Jabal al-Zawiya in Idlib."
British Defence Secretary Michael Fallon, meanwhile, said that just five percent of Russian air strikes had targeted IS fighters.
In Raqa, where IS militants have carried out some of the mass beheadings that they infamously use as online propaganda, activists and residents said the group cancelled Friday prayers and emptied mosques because they feared more Russian strikes.
"The residents are very afraid, especially if the Russians are going to operate like regime planes by targeting civilians," said activist Abu Mohammad, who is from Raqa.
Western nations including France say they are prepared to discuss a political solution with elements of the Syrian regime, but insist Assad must leave power.
Putin, on the other hand, says Assad should stay.
Alexei Pushkov, a Putin ally and senior lawmaker, said the campaign of Russian air strikes will last for three to four months and will increase in intensity. He said more than 2,500 air strikes by the US-led coalition in Syria had failed to inflict significant damage on IS, but Russia's campaign would be more intensive.
Syria's Foreign Minister Walid Muallem said Damascus would take part in UN talks aimed at launching formal negotiations on ending the four-year war but will not be bound by their outcome.
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