Senior officials from former Soviet republics, including Russian President Vladimir Putin, are gathering in Yerevan to attend a session of the Russian-led Collective Security Treaty Organization (CSTO).
In addition to heads of state, the foreign ministers and defense ministers of the CSTO's six member states are in Yerevan for the talks.
The October 14 meeting of the CSTO's Collective Security Council was expected to focus on the election of a new CSTO secretary-general, as well as joint efforts to combat terrorism.
As leaders gathered in Yerevan, Armenia formally transferred its chairmanship of the CSTO's Council of Foreign Ministers to Belarus.
The CSTO is a regional security group of former Soviet republics that includes Russia, Belarus, Armenia, Kyrgyzstan, Tajikistan, and Kazakhstan.
Kremlin aide Yury Ushakov has said that the talks in Yerevan will be attended by the leaders of all member states except Kazakhstan.
Astana says Prime Minister Baqytzhan Saghyntaev will represent Kazakhstan in place of the 76-year-old President Nursultan Nazarbaev, whose visit to Yerevan was canceled because of what Nazarbaev's aides have described as "a cold."
On October 13, a group of Armenian protesters raised a banner on the roof of the newly built CSTO Academy in Yerevan, calling for Putin to stay out of Armenia.
Protester Davit Sanasaryan, a member of the opposition Heritage party, told RFE/RL the CSTO was a "Russian power organization" that does nothing to improve Armenia's security.
With reporting by TASS and Interfax