The UN Register of Conventional Arms has informed that Russia sold 10 tanks, 25 attack helicopters, and 438 artillery systems to Azerbaijan in 2013. 

According to the report, overall, Azerbaijan has received a total of 72 tanks, 34 armored vehicles, 456 artillery systems, 37 attack helicopters, and 1,200 rockets and missile systems from Russia.

By comparison, official Moscow sold 35 tanks, 110 armored vehicles, 200 rockets or missiles, and 50 launchers used for them to Armenia last year.

To note, Russia is a mediator in the Nagorno-Karabakh peace process, and Armenia's strategic ally.