The World Health Organization has urged Russia to follow international guidelines for producing a vaccine against Covid-19 after the country said it would begin vaccinations in October.
"Sometimes individual researchers claim they have found something, which is of course, as such, great news," WHO spokesman Christian Lindmeier told reporters on Tuesday.
"But between finding or having a clue of maybe having a vaccine that works, and having gone through all the stages, is a big difference."
Last week, the Russian government announced it was preparing to begin mass vaccinations.
However, the Russian vaccine is not among the WHO's list of six vaccines that have reached phase three clinical trials, which involve more widespread testing in humans.