"The controlling stake in this fund will be held by Russia," Dmitry Medvedev told journalists.
The $10 billion fund is being established to counter problems in the economy and finances of Eurasec member states.
Belarusian President Alexander Lukashenko said Wednesday Russia and Kazakhstan would contribute $7.5 billion and $1 billion respectively to the Eurasec anti-crisis fund.
Lukashenko, who is chairing an extended session of the Eurasec interstate council, said the money would be allocated to those members of the Community facing grave social and economic problems.
He also said the next summit of the post-Soviet economic organization would take place in Minsk, the capital of Belarus, in October or November.
The Eurasian Economic Community, established in 2000, comprises Belarus, Kazakhstan, Kyrgyzstan, Russia and Tajikistan. Three other former Soviet republics, Armenia, Moldova and Ukraine have observer status.