Russian President Vladimir Putin in a conversation with his Turkish counterpart Recep Tayyip Erdogan has expressed deep concern over the the increasingly extensive involvement of terrorists from the Middle East in Nagorno-Karabakh clashes, Kremlin's website reports.

In the phone talks initiated by the Turkish side, the two discussed recent events in the zone of the Karabakh conflict.

"The Russian side expressed deep concern over the ongoing hostilities, as well as the increasingly extensive involvement of terrorists from the Middle East in clashes," the Kremlin said.

"Vladimir Putin informed [Erdogan] about his communication with the leaderships of Azerbaijan and Armenia and the steps being taken in order to reach a ceasefire as soon as possible and de-escalate the crisis."

Turkey has active military presence in the war against Artsakh (Karabakh). Turkish troops support Azerbaijan, while Ankara is transferring mercenaries from Libya and Syria to fight against Karabakh.

Armenia was the first to report on Turkey's deployment of thousands of Syrian fighters to Azerbaijan. International media publications followed suit, as did reactions from France, Russia Iran and Syria.

Azerbaijan, with help from Turkey and Syrian and Libyan mercenaries deployed by Ankara, started a war against Karabakh (Artsakh) in the morning of September 27. The Armenian side has reported deaths and injuries both among the civilian population and the military. Foreign and local journalists too have been injured in Azeri shelling of towns and villages.