New variants of Covid-19 are suspected of causing a sudden jump in the number of cases in the Russian capital, the mayor said Thursday, amid a sluggish vaccination drive.

"It's most likely we are facing new, more aggressive variants which spread more quickly," said mayor Sergei Sobyanin during a video conference with government officials battling the pandemic.

He noted that daily infections in the capital had soared from 3,000 to 7,000 within a few days and were expected to hit more than 9,000 on Friday.

"It's tripling, there's an enormous dynamic that we have not seen during the previous waves," Sobyanin added.

The mayor had on Wednesday ordered mandatory vaccinations for Moscow residents working in the service industry, citing a "dramatic" rise in coronavirus infections.

Some 60 percent of all service industry workers in Moscow -- just over two million people -- were ordered to be fully vaccinated by August 15, including taxi drivers, staff at cultural venues and restaurant workers.

Sobyanin on Saturday announced this week was a "non-working" week in the capital to try to control the virus.

Moscow health officials have in recent weeks reported a steady rise in the number of new infections, mirroring a trend across Russia.

Health Minister Mikhail Murashko told the video conference the number of cases across Russia had climbed an average of 30 percent in recent weeks and people aged 30-40 were particularly affected.

"The proportion of the Indian (Delta) variant has clearly progressed over the last two weeks," added Anna Popova, head of the health watchdog Rospotrebnadzor.

The increase in cases comes as authorities struggle to encourage Russians to get vaccinated, even though the country launched a mass campaign of free jabs in December.

Sobyanin, whose city of some 12 million is the epicentre of the outbreak in Russia, said just 1.8 million residents had been inoculated.

Since December only 19 million out of a national population of 146 million have received at least one dose of a vaccine, according to the Gogov website which tallies Covid figures from the regions and the media in the absence of a national statistics office.

Russia overtook Britain on Thursday as the European country to record the most Covid deaths with 127,992.

However the Rosstat statistics agency, which uses a broader clinical definition of fatalities linked to Covid-19, says at least 270,000 Russians have died from coronavirus.