Moscow health authorities have revised the city’s coronavirus death toll for April, revealing that more than twice as many people died than previously reported.

Officials raised the documented number of fatalities attributed to Covid-19 to 1,561 up from 636.

CNN and other news outlets reported in mid-May that Moscow saw a mortality spike in April, adding an estimated 1,800 excess deaths in comparison with previous year averages.

Russia’s official number of Covid-19 deaths has been relatively low compared to countries with similar numbers of overall infections, and observers have questioned official counting methods that permit ascribing deaths in patients who tested positive for coronavirus to other causes such as terminal illnesses and other underlying conditions.

In the report, the city health department said it revised the toll according to new counting guidelines and included even the “most debatable” cases in its overall figures.

The report reveals that, in addition to the initially reported 636 fatalities, another 756 people who tested positive for coronavirus died in April. Their deaths were originally ascribed to other causes, but for some, “the virus became the catalyst for the main condition” and its lethal complications, the report states.

Authorities also added 169 deaths to the toll to include people who tested negative for coronavirus, but for whom coronavirus was established as the main cause of death through post-mortem examination. 

Moscow authorities said that, even with a revised death toll, the Russian capital’s mortality rate from Covid-19 remains lower than in other comparably large cities such as London and New York. 

City officials as well as Russia’s central government have warned the public the numbers for May will be higher.

Russia’s regions have mostly followed Moscow’s lead in its response to the pandemic as well as with counting cases, so revising the counting method may lead to an increase in the death toll across the country. 

Some regions have been reporting “double statistics,” releasing numbers of deaths in coronavirus-positive patients that have been officially ascribed to other causes in national figures. 

Officials in Dagestan, one of the worst hit areas in Russia, have previously said publicly their overall death toll was much higher than what is reflected in federal statistics.