TBILISI, March 6 (Reuters) - 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.

Azerbaijan said Russia had "distorted facts" in its account of the incident and described Armenian explanations of the confrontation as "hypocritical".

Russia's defence ministry said Azerbaijani troops had fired on a car carrying local law enforcement officials in the region, killing three and injuring another. In return fire, the pro-Armenian officials killed two Azerbaijani troops, it 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 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.

"We urge the parties to show restraint and take steps to de-escalate the situation," Russian Foreign Ministry spokeswoman Maria Zakharova said in a statement. "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 the clash and said it was working with both Azerbaijani and Armenian officials to establish what happened.

"The incident once again confirms the imperative need for Baku and Yerevan to resume negotiations as soon as possible," Zakharova added.

Azerbaijan's Defence Ministry dismissed any notion that Russia had offered assistance during the altercation, saying its own forces had evacuated dead and wounded servicemen.

It repeated allegations that Armenia violated agreements by routinely transporting mines and weapons into Nagorno-Karabakh.

"In order to prevent similar situations, the Russian peacekeeping contingent must immediately fulfill its duties," it said.