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Moscow is mobilising more forces to fight hundreds of wildfires raging across a vast area of central Russia amid a record heatwave.

At least 40 people have died in fires in the past week, and seven regions are under a state of emergency.

Some fires are in danger of getting out of control, the government said.

Officials say a naval aviation storage area outside Moscow burnt down last week, with the loss of an unknown quantity of hardware.

Nobody was hurt but 13 warehouses were destroyed in the blaze near Kolomna, which began on Thursday and lasted into Friday, military prosecutors said.

According to Russian news agency Interfax, the Kolomna depot services aircraft from all of Russian navy's fleets.

Earlier, the defence ministry denied Russian media reports that scores of planes and helicopters had been destroyed.

Elsewhere, extra firefighters went to protect a major nuclear facility at Sarov, in the Nizhny Novgorod region. It was a top secret site in the Cold War.

Many children are also being evacuated from summer camps threatened by fires.

About a fifth of Russia's grain crop has been destroyed and there was another big rise in the price of wheat on international markets on Monday.

No let-up in the record heatwave is expected in the next few days. Temperatures in the Moscow area are expected to hit about 38C (100F) this week.

At a meeting with President Dmitry Medvedev, Emergencies Minister Sergei Shoigu said firefighters had managed to protect 360 populated areas in danger of forest blazes.

But he warned that the situation was dangerously unpredictable.

"In some places it is getting out of control and urgent firefighting manoeuvres are needed," he said.

About 155,000 people, including 124,000 emergency workers, and more than 20,000 units of machinery are currently being used to fight the fires across Russia, the minister said.

Most of 323 new fires which flared up on Monday were put out.

However, 529 fires continued to burn on Tuesday over an area of 172,300 ha (425,762 acres), compared with 460 on Monday.

Mr Shoigu confirmed that many of the fires were caused by human negligence.

An eyewitness travelling in forested areas east of Moscow over the past week told the ´óÏó´«Ã½ she had seen smokers on a train flick smouldering cigarette butts from windows, and motorists likewise discarding them along roads.

The head of the ministry's crisis centre, Vladimir Stepanov, said municipal bodies in central Russia "must mobilise all their forces, not just sit and wait for fire brigades to arrive".

Russian officials say more firefighters are being deployed south of the Sarov nuclear research centre as a precaution.

More than 2,000 people fought a blaze in the area on Monday and 1,000 were still at work on Tuesday in conditions of poor visibility, Mr Shoigu said.

"We hope to bring the situation by Tuesday evening to the level observed the day before yesterday," he added.

Thousands of people have lost their homes in 14 regions of Russia, the worst-hit being Nizhny Novgorod, Voronezh and Ryazan.

Nineteen of the 40 deaths recorded were in Nizhny Novgorod, the health ministry said.

The state of emergency was announced in a decree that also restricted public access to the regions affected.

Peat bog fires outside Moscow have shrouded the capital in smog for several days. Doctors say the elderly and toddlers should wear gauze masks outdoors.

More famous for its bitterly cold winters, the giant country's European part normally enjoys short, warm summers.

However, this July was the hottest month on record, with Moscow, which sees an average high of 23C in the summer months, sweltering in 37.8C heat last Thursday.