POLITICO reports that it has seen leaked documents showing that Belarus delivered advanced weapons to Azerbaijan between 2018 and 2022.

POLITICO points out that Belarus and Armenia are members of the Moscow-backed Collective Security Treaty Organization (CSTO), and that theoretically members are obliged to defend each other if attacked.

The U.S.-based digital newspaper says the cache of more than a dozen letters, diplomatic notes, bills of sale and export passports shows Belarus actively aided Azerbaijan’s armed forces by modernizing older artillery equipment and providing new gear for electronic warfare and drone systems.

Azerbaijan effectively used drones in the 2020 Artsakh War and in its September 2023 offensive that ended the de facto independence of Nagorno Karabakh.

The Armenian government, noting CSTO’s inaction when Azerbaijani forces launched incursions into the country in September 2022, has suspended its participation in the military bloc and has warned it will withdraw from it altogether.

Armenian PM Nikol Pashinyan, on Thursday, said that no official from Armenia will visit Belarus and that Belarus President Alexander Lukashenko should apologize to the Armenian people.

Earlier, Armenia ordered its ambassador in Belarus to return to Yerevan for consultations. In return, Belarus recalled its ambassador to Armenia, also for consultations.

One of the diplomatic communiques seen by POLITICO says Belarusian enterprises were playing an active role “in the restoration of de-occupied territories of Azerbaijan, as well as the export of Belarusian goods and services” to the country.