Russia called for an immediate end to heavy fighting which continued on the Armenian-Azerbaijani border for the second consecutive day on Monday, per Azatutyun.

Russian Foreign Minister Sergey Lavrov phoned his Armenian and Azerbaijani counterparts to discuss the tense situation there.

“We find inadmissible a further escalation threatening the security of the region,” the Russian Foreign Ministry said in a statement. “We are calling on the conflicting sides to show restraint and strictly adhere to the ceasefire regime.”

“For its part, the Russian Foreign Ministry is ready to provide necessary support for stabilizing the situation,” added the statement.

Three Azerbaijani soldiers were killed and several others wounded shortly after the fighting broke out at a western section of the long border in disputed circumstances on Sunday afternoon. It continued overnight, leaving another Azerbaijani serviceman dead. The Armenian army reported no combat deaths within its ranks.

Both sides reported on Monday morning continuing skirmishes involving mortar fire. The Defense Ministry in Yerevan claimed that Azerbaijani forces also used an attack drone and shelled an Armenian border village.

Each side again accused the other of provoking the escalation with attempts to seize enemy positions in the mountainous area between Armenia’s northern Tavush province and the Tovuz district in western Azerbaijan.

Prime Minister Nikol Pashinian condemned Baku’s “provocative actions” during a cabinet meeting in Yerevan. “I can assure you that their provocative actions do not remain unanswered,” he said, appealing to the nation.

Meanwhile, Azerbaijani President Ilham Aliyev held an emergency session of his national security council to discuss the deadly truce violations. “We thwarted the [Armenian] attack and gave an adequate response, avenging the death of our soldiers,” he said, according to the Trend news agency.

Foreign Ministers Zohrab Mnatsakanian of Armenia and Elmar Mammadyarov of Azerbaijan stood by their countries’ official versions of events during their separate phone conversations with Lavrov. Mammadyarov also said that the fighting is contributing to “third countries’ involvement in the Armenian-Azerbaijani conflict.”

It was not clear if Mammadyarov referred to Russia or Turkey, his country’s closest ally. Ankara was quick to blame Yerevan for the latest escalation and reaffirm its unconditional support for Baku.

Earlier in the day, the secretary general of the Collective Security Treaty Organization (CSTO), Stanislav Zas, called an emergency meeting of the Permanent Council of the Russian-led defense alliance, of which Armenia is a member, to discuss the situation on the Armenian-Azerbaijani frontier.

The meeting was postponed indefinitely a couple of hours later, however. A spokesman for Zas refused to say who initiated the delay. He only told RFE/RL’s Armenian service that the CSTO Secretariat and member states need to ascertain the “format” of the discussion beforehand.

Zas and Mnatsakanian also spoke by phone on Monday. “Constant contact with the CSTO Secretary General is maintained, and efforts within the CSTO framework are continuing,” said the official Armenian readout of the phone call.