Azerbaijan and Armenia exchanged accusations on April 23 over alleged military supplies and the appearance of checkpoints in a sensitive region around the Caucasus foes' shared border.

In a move condemned by Armenians in Nagorno-Karabakh, Azerbaijani authorities on April 23 set up a border checkpoint on the only road connecting the mostly Armenian-populated region with Armenia.

In setting up the border checkpoint at the Lachin road, Azerbaijan's State Border Service said that it mirrored a similar unilateral step by Armenia made on April 22.

In Baku, the Foreign Ministry said Azerbaijan called its action a "legitimate decision" and that it "took appropriate measures to establish control at the starting point of the road."

"Ensuring border security...is the prerogative of the government of Azerbaijan and a necessary condition for national security, state sovereignty, and the rule of law," it added.

The checkpoints are intended to restrict traffic on the only road connecting Armenia with the mostly Armenian-populated parts of Azerbaijan's breakaway Nagorno-Karabakh region.

The "frozen conflict" erupted violently in 2020 into intense fighting that lasted six weeks before a Russia-brokered cease-fire resulted in Armenia and ethnic Armenians losing control over parts of the region and seven adjacent districts.

Tensions have flared recently as the Lachin Corridor has been blocked by government-backed Azerbaijani protesters since December 2022.

The availability of food in Nagorno-Karabakh has become acute due to irregular deliveries, and prices for food and other goods have risen significantly and there have been interruptions in supplies of gas and electricity.

On April 23, Azerbaijan's State Border Service accused the Armenian side of shuttling "continuing military supplies from Armenia to Nagorno-Karabakh," a claim repeatedly denied in both Yerevan and Stepanakert.

The Armenian side has, for its part, accused Azerbaijan of seeking a pretext for isolating Karabakh Armenians.

Ethnic Armenian leaders in Nagorno-Karabakh have also accused Baku of violating the terms of the Moscow-brokered 2020 cease-fire agreement, under which the road passing through the 5-kilometer-wide area known as the Lachin Corridor should be under the control of Russian peacekeepers.

The U.S. State Department said in a statement on April 23 that it was "concerned that Azerbaijan's establishment of a checkpoint on the Lachin Corridor undermines efforts to establish confidence in the peace process."

"We reiterate that there should be free and open movement of people and commerce on the Lachin Corridor and call on the parties to resume peace talks and refrain from provocations and hostile actions along the border," it added.

Armenia's Foreign Ministry on April 23 said the Azerbaijani roadblock "grossly violated" the terms of the 2020 cease-fire deal.

“We call on the Russian Federation to finally fulfil its obligation under Provision 6 of the trilateral statement by eliminating the illegal blockade of the Lachin corridor and ensuring the withdrawal of Azerbaijani forces from the entire security zone of the corridor,” the Armenian ministry statement said.

The latest incident comes a day after Azerbaijan's Ministry of Defense said three soldiers were injured when their vehicle was blown up on a mine allegedly supplied from Armenia.

In another statement, the ministry claimed that Russian peacekeepers controlling the area again helped Armenians transport "military cargoes" from Armenia to Nagorno-Karabakh via the Lachin road.

Armenian has denied both accusations.

Separately on April 23, Armenia's Defense Ministry said one of its soldiers was killed by an Azerbaijani sniper near the border. Azerbaijan denied the allegation and said its soldiers had come under fire from in the border area.

Speaking in parliament earlier this week, Armenian Prime Minister Nikol Pashinian said Armenia recognizes Azerbaijan’s territorial integrity and is ready to sign a relevant peace treaty with Baku.