Moscow sells weapons to Armenia and Azerbaijan but has also led attempts for a truce.
Azerbaijan has said its forces shot down a Russian helicopter near its border with Armenia by accident, expressing apologies to Moscow and readiness to pay compensation.
“The Azerbaijani side offers an apology to the Russian side in connection with this tragic incident,” the foreign ministry said in a statement on Monday, adding the move was an accident and “not aimed against” Moscow.
It came shortly after Russia said one of its Mi-24 helicopters was downed in Armenia, killing two servicemen and wounding another.
The defence ministry in Moscow said in a statement that the helicopter was hit by a man-portable air-defence system and launched an investigation to determine who was responsible for the act.
Azerbaijan’s foreign ministry said the helicopter flew at a low altitude during hours of darkness and close to the state border between Armenia and Azerbaijan.
“Helicopters of the Russian air force had not been previously sighted in the area,” it added.
Azerbaijan said its forces decided to open fire due to heightened tensions amid intense fighting with Armenian forces over the disputed region of Nagorno-Karabakh.
Russia, which held vast influence in the South Caucasus during Soviet times, has a defence pact with Armenia but also has good relations with Azerbaijan.
Moscow has said it would only intervene if fighting reached Armenian soil after Armenian Prime Minister Nikol Pashinyan formally asked Russian President Vladimit Putin to begin “urgent” consultations on security assistance.
On Saturday, Putin spoke to his Turkish and French counterparts, Recep Tayyip Erdogan and Emmanuel Macron, respectively.
Turkey is a major ally of Azerbaijan and its involvement would be key to any agreement to halt the fighting.
Meanwhile, ethnic Armenians in Nagorno-Karabakh earlier on Monday confirmed the loss of the disputed region’s second-biggest city to Azerbaijani forces.
“We have to admit that a chain of failures still haunts us and the city of Shushi (known as Shusha in Azerbaijan) is completely out of our control,” Vahram Poghosyan, a spokesman for the ethnic Armenian Nagorno-Karabakh leader, said in a statement on Monday, adding that Azerbaijani forces were closing in on the disputed region’s main city.
“The enemy is on the outskirts of Stepanakert,” he said, “and the existence of the capital is already in danger.”
Armenian and Azerbaijani forces have been fighting for six weeks in the region of Nagorno-Karabakh, which is within Azerbaijan but has been under the control of ethnic Armenians since 1994.
More than 1,000 people have been reported killed in the conflict.