Azerbaijan said it set up a checkpoint on Sunday on the Lachin corridor, the only land link between Armenia and the disputed Nagorno-Karabakh enclave.

The two ex-Soviet Caucasus nations have fought two wars over Azerbaijan’s Armenian-majority region of Nagorno-Karabakh.

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.

Baku and Yerevan went to war in 2020 and in the 1990s over Nagorno-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.

Azerbaijan, however, said it set up the checkpoint at 12:00 pm (0800 GMT) 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 claim was illegal mining.

Yerevan accused Baku of staging the demonstrations and creating a humanitarian crisis in the mountainous enclave.

Armenia has also accused Russia, embroiled in its Ukraine offensive, of failing to prevent the blockade.