Moscow and Damascus were not behind an air strike in Syria last week that killed four Turkish soldiers, Russian Foreign Minister Sergei Lavrov said on Thursday, refuting Turkish claims.

"Neither Russia nor Syria, its air force, had anything to do with this," Lavrov told a news conference in the southern Turkish resort of Alanya, alongside his Turkish counterpart Mevlut Cavusoglu.

"Our (Russian and Turkish) representatives had discussed this issue right after the incident on various levels," he said.

Turkey blamed Syria for the November 24 strike, which came on the first anniversary of the shooting down of a Russian military warplane by the Turkish air force.

That incident sparked an unprecedented crisis in relations between Turkey and Russia, who remain on opposite sides of the Syrian conflict.

Ankara is staging an unprecedented military operation in northern Syria to support rebels against Islamic State (IS) jihadists.

With Turkey's help, opposition fighters have so far retaken Jarabulus, Al Rai and the symbolically important town of Dabiq from IS.

Moscow has sided with Syrian President Bashar al-Assad, providing military support that the Western observers say is killing civilians, not just jihadists and the rebels.

Russian President Vladimir Putin and Turkish counterpart Recep Tayyip Erdogan discussed Syria three times on the phone in the last week including the Turkish soldiers' deaths.

Lavrov warned that coordination between Moscow and the US-led coalition was key to improving the fight against terrorists.

"We coordinate with the US-led coalition, of which Turkey is a part, with the goal of avoiding unplanned incidents. So, through these channels, it would make sense to check who was flying and who was not flying."

- Humanitarian corridors in Aleppo -

Lavrov also defended Moscow's involvement in a massive Syrian bombing campaign to crush the last resistance by rebels in eastern Aleppo, which has forced thousands of civilians to flee.

"We have helped the Syrian regime to thwart attempts by terrorists to block the exit of civilians from eastern Aleppo," Lavrov said in Alanya.

Lavrov said Russia used any opportunity to help civilians despite what he said "threats from those called local council to prevent passage of humanitarian convoys and fire on them."

The UN reported Thursday Russia proposed setting up four humanitarian corridors to eastern Aleppo to allow aid to enter and to evacuate the injured.

- 'Meetings with Syrian opposition' -

Lavrov added now that "most of eastern Aleppo has been liberated", he did not understand why large-scale efforts to organise humanitarian convoys had not yet begun despite talks with the United Nations.

Lavrov also confirmed "ongoing" meetings with the Syrian opposition "to convince them to become part of the solution" but declined to comment on its details.

"We never evaded contact with all opposition groups," he stressed.

For his part, Turkish Foreign Minister Mevlut Cavusoglu called for a "ceasefire" in Syria and for humanitarian aid to be sent to the country.

He later added: "A political solution is the best solution."