Belarusian acting minister of health Dmitry Pinevich told journalists that the trials took place thanks to direct agreements between the leaders of the two countries - Russian President Vladimir Putin and Belarusian President Alexander Lukashenko.
Belarus reported that 100 volunteers were given the vaccine injections and now their condition is being monitored.
Russia has pushed ahead with its potential COVID-19 vaccine at top speed with mass public vaccinations taking place alongside the main human trial, raising concerns among some observers that it was prioritizing national prestige over solid science and safety.
The first of 5,000 volunteers was vaccinated on Sept. 9, which means interim results could be issued sometime after Oct. 21. Russia's sovereign wealth fund, which has invested in the vaccine's roll-out, has said it expects interim results to be published in October or November.