Russian President Vladimir Putin hosts two summits on May 15 as the CIS Collective Security Treaty Organization (CSTO) marks an anniversary and CIS leaders gather for an informal meeting.
The CSTO summit is devoted to the 20-year anniversary of the signing of the treaty and the 10-year anniversary of the creation of the organization.
The Kremlin press service said all the leaders from the CSTO countries will be present, including Uzbekistan's President Islam Karimov, who has often missed CSTO events in recent years. The other members are Armenia, Belarus, Kazakhstan, Kyrgyzstan, Russia, and Tajikistan.
The informal summit of CIS leaders is due to start after the CSTO meeting ends.
The Kremlin press service said the CIS meeting would have "no fixed agenda" but added "much attention will be given to the deepening of economic integration on the commonwealth space."
These are the first summits of the two organizations since Putin's reelection as Russia's president.
Meanwhile, the presidents of Belarus and Kazakhstan said they had reached a "unity of viewpoints" regarding international issues and the economic union involving their nations and Russia.
The joint statement on May 14, issued during Kazakh President Nursultan Nazarbaev's visit to Belarus, comes after Belarusian President Alyaksandr Lukashenka in April accused Nazarbaev of blocking progress on creation of a Eurasian economic union.
This union, planned to be established by 2015, would also include Russia and would be aimed at facilitating the free movement of services, capital, workers, and goods between the three countries.
The joint Kazakh-Belarus statement also mentioned Kazakhstan's support for Belarus gaining observer status in the Organization of the Islamic Conference, which Kazakhstan currently chairs.
Based on reporting by ITAR-TASS, Interfax, and RFE/RL's Belarus Service