Doctors in Moscow are being told not to diagnose heatstroke as a cause of death after a jump in the mortality rate during the heatwave, Russia media say.
Speaking on condition of anonymity, one doctor said the unofficial instruction being passed down was to use diagnoses that "sound less frightening".
A photo shows a note pinned up in a casualty area which reads "Attention! Do not diagnose heatstroke".
While wildfires continue to burn, temperatures are starting to drop.
The emergencies ministry reported that as of Thursday morning 66 major fires continued to burn across Russia, 40 of them in peat bogs, which are notoriously difficult to extinguish.
While wildfires continued to burn up to 100km (60 miles) away from the site of the Chernobyl nuclear accident in Ukraine, experts said there was little danger of serious radioactive contamination.
Russian President Dmitry Medvedev said the fires had destroyed a quarter of the agricultural land where cereals are grown.
Speaking in southern Russia at a meeting on stabilising the grain market, he said rises in the price of foodstuffs must be avoided. Russia has already suspended exports of wheat.
'Off the scale'
The number of people said to have been killed by the fires directly stands at 54 after two security personnel died fighting flames near the Sarov nuclear research centre in Nizhny Novgorod.
But little has been revealed officially about the number of people who succumbed to temperatures approaching 40C (104F) and choking smog from the fires.
National mortality figures for the summer have not been reported and when the city of Moscow revealed on Monday that its daily death rate had more than doubled, the federal government swiftly challenged the figures.
A nationwide opinion poll published on Thursday suggested that 75% of Russians believed the main effect of the heatwave had been to exacerbate health problems and push up the mortality rate.
"We have indeed been instructed to stop diagnosing heatstroke," a doctor told Interfax news agency.
"We were told that the figures for heatstroke in Moscow had gone off the scale."
Another doctor explained to the agency that there had been no formal ban: "Everything is done by word of mouth.
"Even though the heatwave is now abating, the informal instruction is in force until 1 September."
Moscow's healthcare department was not available for comment, Interfax added.
Russia's LifeNews website, which published the photo of the note, was similarly unable to get a response.
Upper temperatures in Moscow are forecast to fall just below 30C at the weekend, though this is still well above the August average of 22C.
The sky above the city was clear of smog on Thursday thanks to favourable winds and some success in fighting the wildfires.
"I can finally open the balcony door to let my cat warm in the sun," said economics student Yevgenia Lavrova, 21, told the Associated Press news agency.
"You walk in a street, feel a light breeze and want to breathe again."
How peat bog fires spread
- Peat is formed from decayed vegetation in bogs, moors or swamps.
- Deliberate drainage or drought can expose peat to air.
- Peat can then be ignited by wildfires or spontaneously combust. The air flow allows the peat to continue burning.
- Once alight, the smouldering fire spreads slowly through the peat and can cause the ground above to collapse.