The World Health Organization said any WHO stamp of approval on a Covid-19 vaccine candidate would require a rigorous safety data review, after Russia announced Tuesday it had approved a vaccine.

President Vladimir Putin said Russia had become the first country to approve a vaccine offering "sustainable immunity" against the new coronavirus.

"We are in close contact with the Russian health authorities and discussions are ongoing with respect to possible WHO pre-qualification of the vaccine," said the United Nations health agency`s spokesman Tarik Jasarevic.

A total of 168 candidate vaccines are being worked on around the world, according to a WHO overview published Tuesday.