This has been revealed hours after Armenian Prime Minister Nikol Pashinyan held a late night telephone conversation with President Vladimir Putin. The Armenian government has since confirmed it has requested Russian military assistance to repel Azerbaijan aggression and shelling, according to a statement (machine translation):

"During the meeting, further steps were discussed to counter the aggressive actions of Azerbaijan against the sovereign territory of Armenia that began at midnight. In connection with the aggression against the sovereign territory of the Republic of Armenia, it was decided to officially appeal to the Russian Federation in order to implement the provisions of the Treaty of Friendship, Cooperation and Mutual Assistance, as well as to the Collective Security Treaty Organization and the UN Security Council. 

Armenia is basing the request on the Collective Security Treaty Organization pact it has with Russia, and under which Russia previously sent peacekeeping forces to Nagorno-Karabakh after the Fall 2020 conflict.