Russia on Monday urged Armenia and Azerbaijan to comply with a 2020 ceasefire agreement, expressing "serious concern" about escalating tensions between the two countries over the disputed Nagorno-Karabakh region.
Azerbaijan on Sunday established a checkpoint at the start of the Lachin Corridor, the only road route linking Armenia to Nagorno-Karabakh, in what Armenia called a "gross violation" of a Moscow-brokered 2020 ceasefire agreement between the two sides.
Nagorno-Karabakh is internationally recognised as part of Azerbaijan but largely populated by ethnic Armenians. In 2020, Azerbaijan made significant territorial gains in a six-week war that killed thousands on both sides, before Moscow struck a ceasefire deal that included the dispatch of a Russian peacekeeping force to the region.
Kremlin spokesman Dmitry Peskov told reporters on Monday there was "no alternative" to the 2020 agreement and said Moscow was working with both Baku and Yerevan over the situation.
"Russia is continuing contact, the situation is really difficult," Peskov told reporters.
Russia is an ally of Armenia through a mutual self-defence pact, but also has good relations with Azerbaijan.
While stopping short of directly blaming either side, Russia's foreign ministry in a separate statement highlighted "the unacceptability of any unilateral steps" in violation of the 2020 agreement.
Azerbaijan agreed in 2020 to "guarantee the security of persons, vehicles and cargo moving along the Lachin Corridor in both directions." Armenia says the establishment of a checkpoint at the start of the road is a "gross violation" of those commitments.


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