Russian President Dmitry Medvedev says a customs union joining Russia, Kazakhstan, and Belarus has come into effect after the presidents of the three countries signed documents today.
Medvedev made the announcement at a summit of the Eurasian Economic Community (Eurasec) in Kazakhstan's capital, Astana.
Eurasec unites Armenia, Belarus, Kazakhstan, Kyrgyzstan, Russia, Tajikistan, and Ukraine.
The leaders of Kyrgyzstan and Tajikistan said their countries were also considering joining the customs union.
Eurasec leaders are scheduled to consider the formation of a Eurasec court to replace the Commonwealth of Independent States (CIS) Customs Court and approve a budget for 2011.
Kazakhstan's President Nursultan Nazarbaev announced that the next Eurasec summit will be held in Moscow in late December.
Nazarbaev noted in his opening speech that the group is marking its 10th anniversary.
Medvedev is also scheduled to meet with new Kyrgyz leader Roza Otunbaeva to discuss the recent violence and referendum in Kyrgyzstan.