The Russian capital Moscow was on Thursday hit by smog coming from forest fires in a nearby region in the midst of a summer heatwave.

Several aircraft and over 470 people were working to put out the fires in the Ryazan region, some 250 kilometres (155 miles) southeast of Moscow, the emergencies ministry said.

The region's governor Pavel Malkov estimated on Wednesday that over 800 hectares had been affected by the fires, however the international environmental group Greenpeace put the figure at over 3,300 hectares.

On Thursday morning, Malkov said on social media three fires were still burning over an area of 181 hectares.

"There is a high probability that the fires were caused by human action. And the persistent heat and drought are creating favourable conditions for the fire to spread," Greenpeace said Wednesday.

The NGO said that these forest and peat fires were burning through an area that was already affected by serious fires in 2010, which then caused weeks of suffocating smog in Moscow.

Massive fires have swept through Russia's vast territory in recent years, particularly impacting Siberia, the Arctic and the Far East.

The blazes, which are increasingly frequent, are exacerbated by low rainfall and heat waves that scientists have linked to climate change.

Each summer, these fires release huge plumes of noxious smoke that suffocate towns and cities as far as hundreds kilometres away.

In July 2010, Moscow was suffocated by smoke from peat bog fires resulting in an unprecedented spike in respiratory health complaints and deaths.