Tensions further rose on Sunday when Azerbaijan announced it had opened a checkpoint at the start of the road that leads from Armenia to the ethnic Armenian region of Nagorno-Karabakh that is within Azerbaijan.

Armenia claimed that such a checkpoint violates the pact that ended fierce fighting between the countries in 2020.

Nagorno-Karabakh, which had substantial autonomy under the Soviet Union, came under control of ethnic Armenian forces backed by the Armenian military in 1994 at the end of years of separatist fighting. Armenian forces also took sizable territory surrounding Nagorno-Karabakh itself.

Azerbaijan regained most of the surrounding territory and pieces of Nagorno-Karabakh itself in the six-week 2020 war that killed about 6,800 soldiers.

Under a Russia-brokered armistice, transit along the so-called Lachin Corridor road that connects Nagorno-Karabakh to Armenia was to continue under the guarantee of Russian peacekeepers.

But in December, traffic obstructions began when protesters claiming to be enviromental activists blocked the road. Since then, Nagorno-Karabakh has suffered food shortages and sporadic loss of electricity and gas.

At least seven soldiers were killed in clashes between Armenian and Azerbaijani forces earlier in April.

Armenia claimed a sniper killed one of its soldiers near the village of Sotk. Azerbaijan denied that and said Armenians opened fire with small arms on its forces, who returned fire.

Azerbaijan has repeatedly alleged that Armenians have used the Lachin Corridor to bring weapons and ammunition into Nagorno-Karabakh.