Russia, the world's largest country, reported 17,262 new coronavirus infections nationwide.

Moscow Mayor Sergei Sobyanin extended restrictions which include a ban on public events with more than 1000 people, an 11pm closing time for cafes and restaurants, and the closure of 'fan zones' set up for the European soccer championship.

Sobyanin said earlier this week that Moscow, home to 13 million people, was facing a new, more aggressive and infectious coronavirus variant, and the situation in the city was deteriorating rapidly.

It was not clear if he was referring to the Delta variant, which was first identified in India and has caused a resurgence of cases in Britain.

Kremlin spokesman Dmitry Peskov said President Vladimir Putin was monitoring the situation closely.

Asked to explain the surge in cases Peskov blamed the virus's "cunning nature", a reference to its mutations, as well as "total nihilism, and the low vaccination level".

He rejected the idea, posited by some critics, that Russians were reluctant to have vaccinations because they distrusted the authorities.

As of June 2, the most recent tally available, only 18 million Russians - 12.5 per cent of the population - had received at least one vaccine dose so far.

Moscow authorities this week ordered all workers with public-facing roles to have a vaccination.

Sobyanin said on Friday he expected the city government to start the inoculation of migrant workers with Sputnik Light - a single dose of the Sputnik V vaccine - early next month.

But he also said it was "vitally important" to start administering further booster doses - in effect, a third dose.

He said he himself had just received a top-up, after being fully vaccinated with two doses a year ago. The third doses being offered are a repeat of the first dose of the two-shot Sputnik V vaccine.

Australian Associated Press