Turkey on Wednesday warned Iran and Russia to make their Syrian regime ally stop bombing the rebel-held northern Idlib province, as tensions mounted ahead of mooted peace talks later this month.

Ankara has been working closely with Russia and Iran to end the Syrian conflict over the last months but has stepped up pressure on Moscow and Tehran as the bombardments on Idlib intensified amid fears of a humanitarian catastrophe.

Russia wants to bring all the parties in the Syrian conflict together for a conference in its Black Sea resort of Sochi at the end of this month but the tensions with Ankara are proving a major obstacle.

"Iran and Russia should fulfil their responsibility. If you are guarantors -- and you (Iran and Russia) are -- they should stop the regime," Foreign Minister Mevlut Cavusoglu told the official Anadolu news agency.

Cavusoglu said 95 percent of the violations in Idlib were carried out by the regime and the groups backing the regime.

Idlib province is almost entirely controlled by anti-government forces that are dominated by a jihadist outfit known as Hayat Tahrir al-Sham (HTS) consisting mostly of former fighters from the Al-Nusra Front, an Al Qaeda affiliate.

- 'Sceptical on Sochi' -

Ankara has supported the anti-Assad opposition throughout the almost seven-year Syrian civil war while Russia and Iran have backed President Bashar al-Assad.

However, despite the differences, Turkey had teamed up with the two other powers in a bid to bring a lasting peace to Syria, even though analysts have long warned the three-way alliance is highly brittle.

In the biggest public flare-up of tensions with Moscow and Tehran in months, Ankara summoned the Russian and Iranian ambassadors over the Idlib bombing.

Assad's forces have upped efforts in the last days to impose control over Idlib and the Eastern Ghouta enclave near Damascus, the two last rebel bastions in Syria.

But in the meantime, Russia is hoping to hold a Syria peace congress in Sochi on January 29-30 with the particular aim of setting up a new constitution for post-war Syria.

But Turkey says it will boycott any talks involving Syrian Kurdish militia the Peoples' Protection Units (YPG), which controls much of northeast Syria but Ankara views as a terror group and offshoot of the outlawed Kurdistan Workers Party (PKK).

A previous attempt in November to convene talks in Sochi failed due to disagreements between the prospective participants, in particular Turkey under President Recep Tayyip Erdogan.

"We have said we will not be in any environment... where the YPG is present," said Cavusoglu. A Turkish foreign ministry official told AFP that Ankara's attendance at the talks had not been decided.

Kremlin spokesman Dmitry Peskov said Wednesday "intense contacts" were in progress between Russia, Iran and Turkey in order to draw up the list of participants.

With Iran and Russia themselves not always seeing eye to eye, Russian Foreign Minister Sergei Lavrov held talks Wednesday in Moscow with Iranian counterpart Mohammad Javad Zarif.

Both men emphasised the importance of the Sochi talks, with Zarif saying "we want to move together in the same direction".

"Sochi has failed to land twice and there is still not a lot of clarity about who will go," said one European diplomat, asking not to be named.

"There is a risk it will involve the wrong people at the wrong time," the diplomat added.

Aron Lund, a fellow with The Century Foundation, said: "Russian attempts to smuggle PKK-linked Kurdish groups into the Sochi talks are going to provoke Erdogan, and so he'll push all the buttons he can to stop that".

- 'Letter warning Turkey' -

Alexei Malashenko, Research Director of the Dialogue of Civilizations Research Institute, said that Russia, Turkey and Iran all had different interests in the Syria conflict.

"Yet all three have an interest in a consensus. So they are damned to a consensus," Malashenko, one of the leading Russian experts on the Middle East, told AFP.

Russia is also angered by attacks on the Russian naval base of Tartus and its air base at Hmeimim in Syria last week by drones which Moscow says were sent from Idlib province.

The Russian Kommersant daily said seven military planes were "practically destroyed" but the defence ministry rejected the report.

The ministry has written to Turkish army chief Hulusi Akar and intelligence supremo Hakan Fidan to insist that the terms of a ceasefire are upheld, the defence ministry newspaper Krasnaya Zvezda said.

A likely future sticking point between Russia and Turkey is also the fate of Assad, who Ankara has vehemently opposed throughout the conflict and Erdogan last month described as a "terrorist".

Source: AFP