Azerbaijan has said it set up a checkpoint on the Lachin corridor, the only land link between Armenia and the Karabakh enclave.
Sunday's checkpoint is the first set up by Azerbaijan since the latest war ended in 2020 with a Russian-brokered ceasefire.
"The units of the Azerbaijani Border Service established a border checkpoint on the sovereign territory of Azerbaijan at the entrance of the Lachin-Khankendi road," the state border service said, adding it was a response to a similar move by Armenia.
Tensions between the countries further rose following the announcement with Armenia claiming that such a checkpoint violates the 2020 ceasefire agreement.
Armenia’s defence ministry said Sunday that one of its soldiers was killed by an Azerbaijani sniper near the border, but Azerbaijan denied the claim and separately reported that its soldiers had come under fire from Armenia in another part of the border area.
Baku and Yerevan went to war in 2020 and in the 1990s over Karabakh.
Under the ceasefire that ended the 2020 conflict, Azerbaijan is required to guarantee safe passage on the Lachin corridor, which is patrolled by Russian peacekeepers.
'Transferring firepower'
Azerbaijan said it set up the checkpoint at 0800 GMT (12:00 pm local time) on Sunday "to prevent the illegal transportation of manpower, weapons, mines."
The foreign ministry accused Yerevan of using the corridor for the rotation of army staff, "the transfer of weapons and ammunition, entrance of terrorists, as well as illicit trafficking of natural resources and cultural property."
It said on Saturday it recorded military convoys entering Azerbaijan's territory and "the construction of military infrastructure… at the point closest to the territory of Azerbaijan."
The checkpoint was built "in light of these threats and provocations" and "shall be implemented in interaction with the Russian peacekeeping force."
Tensions had been brewing around the Lachin corridor since last year.
In December, Azerbaijani activists blocked the Lachin corridor to protest what they say was illegal mining.
Yerevan accused Baku of staging the demonstrations and creating a humanitarian crisis in the mountainous enclave. It has also accused Russia, embroiled in its Ukraine offensive, of failing to prevent the blockade.