At least 35 people have been killed and dozens injured in Russia amid forest fires and hurricane-like winds, officials said Friday.

'The situation is very grave,' President Dmitry Medvedev said, according to the news agency Interfax.

He has ordered the deployment of 2,000 soldiers in addition to the 240,000 firefighters already struggling to douse the flames. Planes and helicopters are also being used across the country.

The area around St Petersburg, meanwhile, was hit by a violent storm. Seven people, including two children, were killed by falling trees.

July has been the hottest month on record in 130 years, with temperatures averaging 35 degrees Celsius for weeks in many regions. Russian firefighters have blamed a lack of rain for the spread of the forest fires.

Hundreds of houses have gone up in flames and thousands of people have lost their homes.

In the far east of the country alone, 20 fires are raging across 11 hectares of land, the civil defence ministry said.

Prime Minister Vladimir Putin Friday travelled to the Nishni Novgorod region, around 400 km east of Moscow, where fires have been particularly bad.

State television showed him standing among the smoking ruins of more than 300 houses - most of which had been made of wood. He promised immediate relief aid amounting to some $165 million.

Presidential advisor Viktor Ishayev slammed the lack of surveillance of forests from the air. It had been apparent in the last few days that the fires were spreading rapidly, Ishayev said, according to the news agency Itar-Tass.

But authorities had failed to act, he said.

Putin also criticised their lack of preparation. There would be harsh consequences for the neglectful behaviour of the authorities, he said.

Authorities are also having to deal with plunderers.

The government has said the damage from the fires could cost billions.

Meanwhile, Moscow has been covered in a thick smog for days as firefighters struggle to put out peat fires in the land surrounding the city.