Moscow: Russia's Sputnik V vaccine against Covid is around 83% effective against the Delta variant of coronavirus, lower than previously thought, Health Minister Mikhail Murashko said on Wednesday.

Authorities blamed a surge in coronavirus cases in June and July on the more contagious Delta variant and the population's reluctance to get vaccinated despite shots being widely available.

"The latest results show that effectiveness is around 83%," the TASS news agency cited Murashko as saying.

Alexander Gintsburg, director of the Gamaleya Institute which developed the vaccine, said on Wednesday in an interview with the Izvestia newspaper that Sputnik V was safe and effective against all strains of the coronavirus.

Russia, which has a population of around 144 million, has approved four domestically produced vaccines. It has recorded almost 6.5 million infections since the start of the pandemic.