MOSCOW, Russia (AFP) — Russian President Vladimir Putin and Turkish leader Recep Tayyip Erdogan met for talks in Moscow on Tuesday as they seek common ground on the deadly fighting in northwestern Syria.

Putin and Erdogan spoke together at the opening of the MAKS international air show on the outskirts of Moscow. They were due later to hold private talks and issue a joint statement.

The meeting came ahead of a 16 September summit in Ankara that will bring together the main foreign players in Syria’s conflict — Putin, Erdogan and Iran’s President Hassan Rouhani.

The fighting in Syria’s northwestern Idlib province is threatening to increase tensions between Russia and Iran, who back President Bashar al-Assad’s regime, and Turkey which supports some rebel groups.

Erdogan said last week that a Russian-backed offensive by Assad’s forces against jihadists in Idlib province “very seriously” threatened Turkey’s national security and was causing a major humanitarian crisis.

Moscow and Ankara last year struck a deal to create a buffer zone around Idlib — the last major province of Syria outside government hands — to avert a full-scale regime assault.

But Assad’s forces have been bombarding the province for months and on 8 August launched a ground offensive.

Clashes between anti-government fighters and regime forces killed 51 combatants on both sides on Tuesday, a war monitor said.

For Erdogan, a key question will be protecting Turkish troops deployed in Idlib.

Syrian government forces have encircled a Turkish observation post in Idlib — one of 12 established by Ankara in the region under the buffer zone deal.

Last week a regime air strike cut off a Turkish military convoy shortly after it crossed into Idlib.

Turkey is also concerned over a potential mass exodus of Syrian refugees from the province, which is on its southern borders.

Kremlin spokesman Dmitry Peskov said Monday that Putin “understands the concerns” of Ankara but insists on the need to counter “the actions of terrorist elements in Idlib.”