Russia said on Wednesday that it had appointed one of its most senior army commanders to lead a peacekeeping force in the disputed Nagorno-Karabakh region, as tensions rise again between Armenia and Azerbaijan. 

Russian peacekeepers were deployed in 2020 to end a war over Nagorno-Karabakh, the second that Armenia and Azerbaijan have fought since the 1991 Soviet collapse. The mountain enclave is internationally recognized as part of Azerbaijan but populated mainly by ethnic Armenians. 

The Russian armed forces said the peacekeepers were now headed by Colonel-General Alexander Lentsov, deputy commander-in-chief of the Russian ground forces. He replaces Major-General Andrei Volkov, a more junior officer. 

No reason was given for the change, announced hours after a telephone conversation between Russian President Vladimir Putin and Armenian Prime Minister Nikol Pashinyan. 

Armenia has voiced increasing frustration that the Russian force has failed to keep open the Lachin corridor, the only land route that links it to Karabakh across Azerbaijani territory. 

Russian media quoted an Armenian spokesperson on Tuesday as saying the country had appealed to the International Court of Justice over Azerbaijan’s installation of a checkpoint on the highway on Sunday, calling it a “flagrant violation” of Baku’s obligation to ensure free movement.  

Azerbaijani Deputy Foreign Minister Elnur Mammadov said the checkpoint was set up in response to “safety concerns in light of Armenia’s continued misuse of the road for the transport of weapons and other illegal activities.” 

He added: “We continue to be in close contact with the ICRC [International Committee of the Red Cross] and the Russian peacekeeping contingent to best facilitate humanitarian access.” 

An Armenian spokesperson did not respond to a request for comment.