• More than a third of cultivable land in Russia destroyed • Wheat prices hit 23-month high on commodities market

This article is more than 10 years old

This article is more than 10 years old

Russia's prime minister, Vladimir Putin, has announced a ban on grain exports after millions of hectares of crops perished in the worst drought in more than a century.

High temperatures, lack of rain and wildfires have devastated more than a third of cultivable land in Russia, the world's fourth largest grain exporter.

News of the ban pushed wheat prices to a 23-month high on commodities markets and raised concerns about a boost in food prices worldwide.

Putin said the ban would last from 15 August to 1 December. "We shouldn't allow domestic prices in Russia to rise, and we need to preserve our cattle and build up supplies for next year," he said.

The announcement came as firefighters continued to battle hundreds of fires caused by the heatwave across European Russia, where daytime temperatures have been well above 30C since June.

Moscow's tabloid press has even speculated that the United States orchestrated the heatwave in order to favour its own grain exporters by blasting Russia with harmful rays from a research station in Alaska.

Wheat and barley have shrivelled, sunflowers have wilted and sugarbeet has barely reached half its normal size.

Officials in Moscow had earlier indicated that they would be able to contain internal grain prices using existing stockpiles. But it appears the government decided to step in to protect the agricultural sector and prevent hikes on the price of bread and other staples – a sensitive political topic in a country where millions of pensioners live on the poverty line.

"It's always good to have a reserve in your pocket," said Putin.

Analysts said Russia's grain output could fall from 100m tons in 2009 to 65m tons this year. Farmers have already begun to slaughter livestock early because they expect to run out of feed.

Putin may have acted to prevent a backlash after public displeasure over the handling of the fires which have killed 50 people and left at least 3,000 people homeless in the last week.

On Tuesday he promised residents of burnt-out villages that he would personally monitor reconstruction of their houses via a live video feed beamed to his home.

Last night he went a step further, writing to a blogger who posted a foul-mouthed tirade about the lack of fire prevention measures near his holiday home outside Moscow.

The blogger – known only as "top_lap" – said that in the Soviet era there had been three ponds, a warning bell and a fire engine in the settlement around his holiday home, but recently they had all disappeared. The situation, he said, was "a total fuck-up".

When a radio presenter challenged Putin to respond, the premier unexpectedly praised top_lap for being "open, direct" and "a man of letters".

"In fairness," wrote Putin, "one must note there haven't been such high temperatures for 140 years including the communist times." But he said he agreed with the blogger's criticisms overall and promised him a new warning bell if he would provide his address.

Russia's emergencies ministry said it had saved 141 villages from destruction during the last 24 hours. A veil of smog over Moscow had mostly dispersed, a day after smoke from peat bog fires enveloped the city.

Abnormally high temperatures are expected to continue for at least another five days.