Russia on Monday expressed “serious concern” over escalating tensions in the Nagorno-Karabakh region, where five people are believed to have died in a firefight between ethnic Armenians and Azerbaijani forces, TASS reported.

The Russian Ministry of Defense reports that Azerbaijani forces opened fire on a car carrying pro-Armenian law enforcement officers in the region on Sunday, killing three people and injuring another. Two Azerbaijani servicemen were also killed after the men in the car opened fire, according to Moscow.

The deadly confrontation came after nearly 3 months of renewed tensions between Armenia and Azerbaijan over Nagorno-Karabakh. This region is internationally recognized as part of Azerbaijan, but is mainly populated by ethnic Armenians.

Baku and Yerevan have fought two bloody wars over control of the region, and dozens of other smaller-scale clashes have taken place in the border area over the past 35 years.

In December, Azerbaijanis who called themselves “environmental activists” blocked the Lachin Corridor, the only road connecting the region to Armenia.

Armenia says the blockade has led to shortages of food and medicine in Nagorno-Karabakh, accusing Azerbaijan of orchestrating ethnic cleansing there. The government in Baku denies the allegations, saying the protesters are opposing illegal mining operations in Armenia.

Russia calls for “restraint” and de-escalation of the situation

In a press release on Monday, Russian Foreign Ministry spokeswoman Maria Zakharova said that “we call on both sides to exercise restraint and take measures to de-escalate the situation.”

She also stated that in recent days, the cease-fire agreements agreed upon by the two sides have been repeatedly violated.

Earlier in the day, the Russian Defense Ministry said its peacekeeping troops had intervened to stop Sunday’s confrontation and that it was in contact with both Armenia and Azerbaijan to find out what happened.

“This incident once again confirms the urgent need to resume negotiations between Baku and Yerevan as soon as possible,” Maria Zakharova said.

In November 2020, Russia sent 2,000 troops to Nagorno-Karabakh to maintain peace in the region as part of a ceasefire agreement signed by Armenia and Azerbaijan.

But after the start of new fighting in September of last year, Armenia repeatedly accused Russian troops of failing to fulfill their obligations. The Kremlin denies the allegations, sparking unprecedented tensions with Armenia, a member of the CSTO, a Moscow-led military alliance.