Russian President Vladimir Putin has met separately with the leaders of Azerbaijan and Armenia as concerns mount over the escalation of fighting around Nagorno-Karabakh.

Kremlin spokesman Dmtiry Peskov was quoted as saying that a joint meeting of all three leaders on Sunday was possible.

Nagorno-Karabakh is a part of Azerbaijan but it and some surrounding territory have been under the control of Armenian soldiers and local Armenian forces since a 1994 cease-fire ended a separatist war. Since then, there have been sporadic clashes, but tensions have risen sharply in the past week as 19 soldiers were killed, 13 of them Azeri.

Years of diplomatic efforts under the auspices of the Organization for Security and Cooperation in Europe have made little visible progress in resolving the dispute.