Moscow's health department said 5,260 people died from the novel coronavirus in the city in May, far higher than the 1,895 deaths reported by Russia's coronavirus crisis response center over the course of that month.
"Covid-19 as a main or an accompanying cause of death was registered in 5,260 cases," the Moscow health department said in a statement on its website.
It said the difference of 3,365 between the previous death toll and the new one was down to changes made by Russia's health ministry in its approach to counting coronavirus deaths.
"New recommendations allowed us to improve the calculation of cases where Covid was the main cause of the death and of those where it became, with a high degree of probability, a catalyst...for other illnesses," the department said.
Russia has the third highest coronavirus case tally in the world at 493,657, but its relatively low death toll of 6,358 has been met with accusations of underreporting deaths from the respiratory disease.
Russia says it has a high number of confirmed infections due to its widespread and comprehensive testing regime. It says more than 13.5 million tests have been performed.