ISTANBUL - The leaders of Turkey, Russia, France and Germany met on Saturday to try to find a political solution to Syria’s devastating civil war, provide access to humanitarian aid and salvage a fragile ceasefire in the country’s last major rebel-held bastion.

Turkish President Recep Tayyip Erdogan welcomed Russia’s Vladimir Putin, France’s Emmanuel Macron and German Chancellor Angela Merkel to the summit on the Syrian conflict, in which more than 360,000 people have been killed since 2011.

“The eyes of the world are on us today... I hope we will act with a sincere and constructive understanding and will not fail to meet their expectations,” Erdogan said as he opened the talks in Istanbul.

It comes a day after seven civilians were killed by Syrian regime artillery fire in the northwestern province of Idlib, according to the Syrian Observatory for Human Rights, the highest death toll since a ceasefire was reached there last month.

Russia, which supports the regime of Syrian President Bashar al-Assad, and Turkey, which backs the rebels, agreed to create a buffer zone around Idlib, but violence has escalated dramatically leading up to the summit.

Turkey and Russia have held talks with Iran on the Syrian conflict in efforts that have often been greeted with suspicion in the West, but Saturday’s summit will be the first to include the EU’s two most significant national leaders.

Turkish presidential spokesman Ibrahim Kalin has said that the primary goal would be to “clarify the steps to be taken for a political solution and to determine a roadmap”.

One key objective is to form a committee to draft Syria’s post-war constitution, seen as a stepping stone to elections in the war-torn country.

A rival United Nations plan for a committee to write the constitution ran aground this week, with UN special envoy Staffan de Mistura, who is also attending the summit, saying Damascus rejected the UN having a role in the selection process.

The Istanbul talks will also discuss extending the ceasefire around Idlib, where aid groups have warned that a military offensive could spark one of the worst humanitarian disasters of the seven-year war.

With an assault by government troops seeming imminent, Moscow and Ankara agreed on September 17 to create a 15-20 kilometre-wide demilitarised zone ringing Idlib as Turkey sought to avoid an attack leading to a further influx of people across its border.

However shelling in the area continued intermittently and has ramped up in recent days. Syria’s UN envoy Bashar Jaafari maintained on Friday that the buffer zone is temporary and that Idlib would eventually revert to government control.

However France hopes to extend the ceasefire to enable aid convoys to get through to Idlib, home to three million people.

After arriving in Istanbul, Macron tweeted that what was at stake was averting a “new humanitarian disaster”.

The participants talked down hopes of a long-term solution ahead of the summit, with the Elysee palace speaking of “modest expectations” and Putin’s spokesman Dmitry Peskov urging all sides to be “realistic”.

Peskov said that while all sides want a political settlement, “certain disagreements may exist regarding the instruments and tactics”, and the day was to “synchronise our watches” and “attempt to identify common topics”.

Syria’s opposition, which has previously described Russia’s military intervention in 2015 as an occupation, on Friday said it welcomed dialogue with Moscow.

However US Defence Secretary Jim Mattis told a security conference in Bahrain that Russia was no replacement for the United States.

The summit also takes place in the aftermath of journalist Jamal Khashoggi’s murder in the Saudi consulate in Istanbul on October 2.

Macron and Merkel discussed the case before the summit, moving to quash a rare dispute between the close allies after the French president implied on Friday that Berlin was engaging in “pure demagoguery” by halting arms sales to Riyadh over the murder.

The two leaders agreed not to announce their next positions on the issue without first coordinating “at the European level”, the Elysee palace said.

Turkish media reported that Erdogan will discuss the Khashoggi case in one-on-one talks with leaders on the summit’s sidelines.