The council of the Moscow-led Collective Security Treaty Organisation (CSTO) will meet via video link on Tuesday evening to discuss the outbreak of hostilities along the Armenian-Azerbaijani border overnight, a Kremlin aide said.
Armenia and Russia are military allies through their membership of the CSTO, but Moscow also strives to maintain friendly relations with non-member Azerbaijan, and acts as a power broker in the South Caucasus region.
Following a request by Armenia, the CSTO council will meet at 1830 Moscow time (1530 GMT), Kremlin aide Yuri Ushakov said at a briefing in Moscow.
The United States and European Union on Tuesday joined Russia in calling for an end to hostilities, which Armenia's Prime Minister Nikol Pashinyan said left at least 49 Armenian soldiers dead.
Both Baku and Armenia have blamed each other for the flare-up in decades-old hostilities between the two countries, linked to the status of the disputed Nagorno-Karabakh region.
President Vladimir Putin spoke to Pashinyan on Tuesday and will meet Azerbaijan's President Ilham Aliyev in Uzbekistan later this week, Ushakov said.
(Reporting by Vladimir Soldatkin, Editing by William Maclean)
