King Carl XVI Gustaf released a statement saying he was “worried” about the fires that are raging in 59 locations in Sweden.
He said: “My family and I are worried about the evolution of events around the large number of fires that ravage around our country this unusually hot and dry summer.
“At the moment, a lot of work is being done to fight the fires and minimise their damage.
“I want to express my and the Royal Family’s support for all of you and to all of you who are affected and affected by the fires.
“To all the people – rescue personnel, defence workers, home care staff and volunteers – who in this strained situation make great sacrifices to help others, I and my family want to say: thank you. Your commitment and your efforts are invaluable.”
The fires have broken out across a wide range of Sweden’s territory north-west of the capital of Stockholm as the hot, dry summer continues to stoke the flames.
Four communities have been evacuated and tens of thousands of people have been warned to keep windows and vents closed to prevent smoke inhalation. Rail services have also been disrupted.
More than 60 fires are burning across Sweden as Norway, Finland and Russia also battle blazes.
Norway and Italy are sending assistance. Six fire-fighting helicopters are being sent from Norway.
Two Canadair CL-415s, which can dump 6,000-litres of water each time, are being sent to central-southern Sweden from Italy.
In the western part of the country efforts were temporarily stopped amid fears of an unexploded bomb that could be detonated in the extreme heat.
Even though wildfires happen every year, these fires have been described as “excessive” after residents in Uppsala have gone 18 consecutive days without rain.
Mike Peacock is a university researcher and a resident.
He said: “This is definitely the worst year in recent times for forest fire. Whilst we get them every year, 2018 is shaping up to be excessive.”
Swedish authorities have warned residents to be braced for more fires as the risk is “extremely high” due to temperatures soaring above 30C.
A European commission official said fires are lasting longer and are happening more frequently.
They said: “There are clear trends of longer fire seasons and frequent critical periods in Europe that are leading to dangerous fire situations.”
A professor of global change ecology an the Open University has said the Arctic and other areas typically didn’t experience fires are now becoming more vulnerable.
Vincent Gauci said: “What we’re seeing with this global heatwave is that these areas of fire susceptibility are now broadening, with the moors in north-west England and now these Swedish fires a consequence of that.
“Both these areas are typically mild and wet which allows forests and peatlands to develop quite large carbon stores,” he added. “When such carbon-dense ecosystems experience aridity and heat and there is a source of ignition – lightning or people – fires will happen.”