Russia expressed "serious concern" on Monday over rising tensions in the Nagorno-Karabakh region, where it said five people had been killed in a shoot-out between ethnic Armenians and Azerbaijani troops on Sunday.
Russia's defence ministry said the Azerbaijani troops had opened fire on a car carrying local law enforcement officials in the restive region, killing three and injuring another. In return fire, the pro-Armenian officials killed two Azerbaijani troops, Moscow said.
The deadly clash comes three months into the latest standoff between Baku and Yerevan over the region.
Nagorno-Karabakh is internationally recognised as part of Azerbaijan but populated mostly by ethnic Armenians. The two countries have fought two bloody wars and staged dozens of border clashes for control of the region over the last 35 years.
In December, Azerbaijanis claiming to be environmental activists started a blockade of the Lachin Corridor, the only road linking Armenia to Nagorno-Karabakh.
Armenia says the blockade has led to food and medicine shortages, and that the protesters are government-backed agitators. Baku denies those claims and says the protesters are campaigning against illegal Armenian mining.
The fresh clash is seen as a key test of Russia's influence in the south Caucasus as it wages its own war in Ukraine.
Moscow deployed thousands of peacekeepers to the region in 2020 to end six weeks of fighting there which killed thousands and saw Azerbaijan make significant territorial gains.
Russia and Armenia are officially allies through a mutual self-defence pact, but Moscow also seeks to maintain good relations with Azerbaijan.
In a statement on Monday, Russian Foreign Ministry spokeswoman Maria Zakharova said: "We urge the parties to show restraint and take steps to de-escalate the situation. Over the past few days there have been repeated violations of the ceasefire regime."
Russia's defence ministry said its peacekeeping forces had intervened to stop Sunday's clash and said it was working with both Azerbaijani and Armenian officials to figure out what had happened.
"The incident once again confirms the imperative need for Baku and Yerevan to resume negotiations as soon as possible," Zakharova added.
(Reporting by Jake Cordell and Caleb Davis; Editing by Mark Trevelyan and Gareth Jones)
