Russia has questioned the neutrality of the European Medicines Agency (EMA) after a senior official urged EU member states not to use the Sputnik V vaccine yet.
During a debate on Austrian television on Sunday, EMA board director Christa Wirthumer-Hoche said it is not known whether the vaccine is safe and effective.
"I strongly discourage the approval of a national emergency authorisation," Wirthumer-Hoche stated, adding that certain European countries that were already using Sputnik V were "comparable to playing Russian roulette".
The Sputnik V vaccine has already been used to innoculate citizens in a number of European countries including Moldova, Montenegro, and Serbia, as well as EU member Hungary. Slovakia has taken delivery of doses and neighbour the Czech Republic will do so at the end of March.
The official Twitter account of the Russian vaccine has condemned the remarks and called for an apology.
"We demand a public apology from EMA’s Christa Wirthumer-Hoche for her negative comments on EU states directly approving Sputnik V," the Gamaleya Centre and the Russian Direct Investment Fund (FIDR) tweeted.
"Her comments raise serious questions about possible political interference in the ongoing EMA review."
Meanwhile, Kremlin spokesman Dmitry Peskov described the EMA official's comments as "distressing" and "at the very least inappropriate".
Last week, the Amsterdam-based EMA began reviewing the vaccine for general rollout in the bloc, after months of criticism from Russia.
Sputnik V's developers have questioned whether the EU regulator has acted politically, and says they are ready to supply vaccines to 50 million Europeans from June.
"Such comments are inappropriate and undermine the credibility of the EMA and its review process," the Gamaleya Centre said on Twitter, "vaccines and the EMA should be above and beyond politics."
"After postponing Sputnik V review for months, the EMA does not have the right to undermine the credibility of 46 other regulators that reviewed all of the necessary data."
The EU initially criticised Russia for registering the vaccine last August before clinical trials had been completed, but a study by the Lancet medical journal in February showed the jab has a 91.6% efficacy against the coronavirus.