A frame grab shows a Russian military jet taxiing on runway shortly after landing in Syria.

AFP, Reuters/Beirut, Paris

At least 12 jihadists from the Islamic State group have been killed in Russia's first air strikes on the extremist faction's main Syrian bastion, a monitoring group said.

Russia's defence ministry confirmed it had carried out strikes on Raqa province on Thursday.

It said Russian Su-34 planes struck "an IS training camp near the village of Maadan Jadid," 70 km east of Raqa city, and "a camouflaged command post at Kasrat Faraj, southwest of Raqa."

The Syrian Observatory for Human Rights said the strikes had killed at least a dozen IS fighters.

"Last night, Russian strikes on the western edges of Raqa city, and near the Tabqa military airport, killed 12 IS jihadists," Observatory head Rami Abdel Rahman said on Friday.

He said their bodies were transported to a hospital in the province.

Moscow's defence ministry said Friday that its war planes had "conducted 18 sorties on 12 positions held by the Islamic State terrorist group in Syria" since Thursday.

The statement said Russian raids destroyed "a command post and communications centre" held by IS in Daret Ezza in northern Aleppo province, as well as bunkers and weapons depots in Maaret al-Numan and Habeet in northwest Idlib province.

Raids also struck "an IS command post" in Kafr Zeita in central Hama province.

According to the Observatory, none of these areas are controlled by IS, though most are held by Al-Qaeda's Syrian affiliate Al-Nusra Front.

And according to a Syrian military source, Russian strikes on Friday also targeted an ancient Christian town in Homs province seized by IS on August 5.

"Russian warplanes struck Al-Qaryatain this morning," the source said.

Air strikes to last three-four months: Putin ally

Russia estimates its air strike campaign in Syria could last three to four months, the head of the lower house of the Russian parliament's foreign affairs committee said on Friday.

"There is always a risk of being bogged down but in Moscow, we are talking about an operation of three to four months," Alexei Pushkov, an ally of Russian President Vladimir Putin, told French radio station Europe 1. He added that the strikes were going to intensify.

Pushkov said the strikes mainly targeted Islamic State forces in spite of reports they had concentrated on opponents to Syrian President Bashar al-Assad.

"The opponents to Bashar are very close to Daesh (Islamic State)," Pushkov said. US sources have said the Russians actually hit facilities of a US-backed group, some of whose rebels received training and support from the CIA.

Pushkov said the US-led coalition had "pretended" to bomb Islamic State forces for a year.

"They pretended... Only 20% of their (US led coalition) operations produced results, 80% of them did not lead to bombardments, they returned to base for different reasons," Pushkov said.

Russia, which launched its first air strikes on Wednesday, has been supporting Assad's regime since the beginning of the conflict in Syria in 2011.

Russian President Vladimir Putin and US President Barack Obama discussed the crisis on the sidelines of the General Assembly on Monday and agreed to start talks to avert military clashes by parallel air campaigns.

Pushkov said there were would be first contacts between US and Russian military officials on Friday to discuss operations in Syria, where the Cold War superpowers are engaged in combat over the same country for the first time since World War Two.

Hundreds of Iranian troops have also arrived in Syria to join a major ground offensive in support of Assad's government, Lebanese sources said on Thursday, a sign the civil war is turning still more regional and global in scope.

Turkey, coalition call for end to  air strikes

Turkey and its partners in the US-led coalition against Islamic State called on Russia on Friday to cease its attacks on the Syrian opposition and focus on fighting Islamist militants, expressing "deep concern" over Moscow's air strikes.

In a joint statement with the US, Britain, France, Germany and Gulf Arab allies, Turkey said Russia's actions constituted a "further escalation" of the conflict and would only fuel more extremism.

"We express our deep concern with regard to the Russian military build-up in Syria and especially the attacks by the Russian Air Force on Hama, Homs and Idlib since yesterday which led to civilian casualties and did not target Daesh," it said.