AFP/ Moscow

Russian military jets carried out strikes on nine Islamic State sites in Syria over the past 24 hours, the defence ministry in Moscow said Monday.

The Russian warplanes hit IS command centres, weapon caches, artillery and communication posts in the Homs, Idlib and Latakia provinces of Syria, the ministry said in a statement.

Russia launched air strikes in Syria last Wednesday in coordination with the Syrian army and says it is hitting targets connected to IS jihadists in the war-torn country.

"25 sorties were completed by Su-34, Su-24 and Su-25 jets from the airbase in Hmeimim. Nine IS facilities were struck," the statement said.

In the northwestern province of Idlib, the Russian military said it had destroyed a training camp by the city of Jisr al-Shughur, artillery positions near Jabal al-Qobeh and armoured vehicles.

A command centre in the coastal region of Latakia was also hit, while in Homs province a command centre near the town of Rastan was struck along with two ammunition depots and a communications centre, Moscow said.

The United States and its allies have accused Russia of seeking to buttress its long-standing ally President Bashar al-Assad under cover of a claimed assault on IS.

Germany on Monday also voiced doubt about Moscow's claims it is targeting IS jihadists with the air strikes rather than moderate rebels.

Russian Foreign Minister Sergei Lavrov said Monday that Moscow had called for fresh contacts with the US over avoiding clashes with the Washington-led coalition fighting IS in Syria.

Lavrov ridiculed the Free Syrian Army (FSA), the main moderate opposition group fighting the Damascus regime, as "something of a phantom", saying that Moscow would be ready to talk to it if it really exists.

"We would even be willing -- if it really is a patriotic opposition armed group consisting of Syrians that still has any capabilities -- to establish contact," Lavrov was quoted as saying by Russian news wires.

"So far no one has told us where and how this Free Syrian Army is functioning."

NATO member Turkey protested to Moscow on Monday after its F-16 jets intercepted a Russian fighter plane that violated its air space near the Syrian border over the weekend, forcing it to turn back.

Kremlin spokesman Dmitry Peskov confirmed that Ankara had summoned Russia's ambassador over the alleged incident.