MOSCOW, September 27. /TASS/. Russian President Vladimir Putin has expressed serious concern over the escalation of the situation in Nagorno-Karabakh, the Kremlin press service said on Sunday after Putin’s telephone conversation with Armenian Prime Minister Nikol Pashinyan.

"The conversation focused on the situation in the zone of the Nagorno-Karabakh conflict. Th Russian side expressed serious concern over large-scale armed clashes. It was noted that it is important now to do everything possible to prevent further escalation of the conflict and stop hostilities," the press service said.

The telephone call was initiated by the Armenian side.

The situation in Nagorno-Karabakh escalated on September 27, when Azerbaijan said its positions had come under extensive fire from Armenia. Armenia, in turn, said the Azerbaijani army had staged ab offensive in the direction of Nagorno-Karabakh. It said a number of settlements in Nagorno-Karabakh, including its administrative center Stepanakert, had come under shelling by Azerbaijan. Both sides report casualties, including among civilians. Armenia’s authorities have imposed martial law and announced mobilization of reservists.

The conflict between Armenia and Azerbaijan over the highland region of Nagorno-Karabakh, a disputed territory that had been part of Azerbaijan before the Soviet Union break-up, but primarily populated by ethnic Armenians, broke out in February 1988 after the Nagorno-Karabakh Autonomous Region announced its withdrawal from the Azerbaijan Soviet Socialist Republic. In 1992-1994, tensions boiled over and exploded into large-scale military action for control over the enclave and seven adjacent territories after Azerbaijan lost control of them. Talks on the Nagorno-Karabakh settlement have been ongoing since 1992 under the OSCE Minsk Group, led by its three co-chairs - Russia, France and the United States.