© Michel Roggo/NPL/Rex FeaturesA brown bear fishes for sockeye salmon in the Ozernaya river, Kamtchatka, Russia, in June last year.
Experts suggest extreme weather could be disrupting biorhythms and food supply, and fishing nets cutting off access to salmon

A rash of bear attacks in Russia have left at least three people dead and many more injured in recent weeks as record high temperatures, freak snow, hailstorms and flooding hit Siberia and the country's far east.

Human activity may be behind some of the attacks. Experts cited by the news agency Interfax said nets and obstacles have prevented salmon from swimming up rivers to spawn, leaving bears without a regular food supply.

Extreme weather can also disrupt the predators' biorhythms and food supply, said Vladimir Krever, director of the biodiversity programme at WWF Russia.

Recent attacks include one at 2am on Wednesday at a meteorological station in the forests of Sakha Republic. A bear broke down the door of a residential trailer and bit the arm of the woman inside, only to be scared away by her loud screaming.

Three days earlier another bear ambushed a boy on Iturup island as he was walking home from his grandmother's house. The bear had dragged the 14-year-old to the shore by the time police arrived and shot it dead. The boy had 170 stitches and remains in critical condition.

This month, a bear killed three construction workers on Sakhalin island and left two in critical condition in an attack that was partially filmed on one of the men's mobile phones. During another attack in the Sakha Republic, a man's mobile phone saved his life when it suddenly activated and the tone scared off a bear that was biting his head. Adult brown bears found in Siberia and far-east Russia can grow to more the 590kg (1,300lbs) in size.

"The increase [in] number of extreme natural phenomena, hurricanes, storms, sudden heat or cold ... can lead to a growth in conflict situations for people in nature, including with bears," Krever said.

A heatwave this month has led to Russia football matches to be delayed and a ceremonial changing of the presidential guard to be cancelled. ThisRecord-breaking temperatures were reported in the Siberian cities of Barnaul, Kemerovo, Novosibirsk and Novokuznetsk.

On 12 July, a heatwave in the Novosibirsk region ended suddenly when the temperature dropped and the area was pelted with egg-sized hailstones, to the horror of beach-goers in one viral video. The same day, a rainstorm turned into a blizzard and left up to 10cm of snow in the Chelyabinsk region owing to what experts said was an Arctic cyclone. Also in July, authorities declared a state of emergency after three months' worth of rain fell in 36 hours in Magadan, cutting off some residents while others wakeboarded behind cars and trucks.

According to Alexey Kokorin, head of the climate and energy programme at WWF Russia, these phenomena are part of a trend he attributed to global climate change, which on top of natural variations has caused the frequency of extreme weather events to more than double in all parts of Russia over the past two decades. "In Russia, all these things have happened, snow in southern Urals and heatwaves in Siberia, but now they're happening more often," he said.