An agreement with Turkey on Syria's Idlib province has not been fully implemented, raising concerns in Moscow and Damascus, the Interfax news agency quoted a Kremlin spokesperson as saying.

Moscow and Ankara have tried to create a de-escalation zone in the region last year, where acts of aggression are expressly prohibited in order to allow the return of thousands of displaced Syrians to their homes.

Last week, Turkish President Tayyip Recep Erdogan went to Moscow to discuss with his Russian counterpart Vladimir Putin the steps needed to stabilise the situation in Idlib.

Russia said that the situation there was rapidly deteriorating and that it was almost under the full control of Hay'et Tahrir al-Sham (HTS) - a rebel group that was previously linked to al-Qaeda.

In September last year, Turkey pledged to disarm and remove HTS fighters in Idlib when a deal was signed between Turkey and Russia.

The deal succeeded in preventing a Russia-backed Syrian government offensive from launching in Idlib which is home to nearly three million people, including many internally displaced persons (IDPs).