Russia was facing \"extremely serious\" wildfires which had already claimed lives, Prime Minister Dmitry Medvedev said Friday, dpa quoted Interfax news agency as reporting. The fires were not only the result of a heat wave and a lack of rain, but were also caused by careless behaviour, he said. More than 3,000 firefighters were battling the blazes, while Tomsk airport in Siberia had to be closed due to smog. Two years ago, several hundred wildfires broke out across Russia, claiming hundreds of lives and causing billions of dollars worth of damage, in what was one of the hottest summers on record. Environmental groups accuse Moscow of not having effective plans to prevent the fires.