More than 50 wildfires — 10 more than the previous day — are now alight across central and western Sweden, but also above the Arctic Circle, authorities confirmed on Friday.
Sweden's head of civil defense Dan Eliasson said fire crews were struggling to bring the most ferocious forest fires in years under control.
He said four of the fires had become too large for firefighters to extinguish. And with no rain in sight, the situation was unlikely to improve over the weekend, he said.
"We will not be able to extinguish the largest fires," Eliasson said. "In these cases, rescue services are working to minimize the spread of the flames and wait until the weather changes."
Large numbers of evacuations have taken place over the past two days, and thousands more residents have been ordered to keep their windows shut to avoid breathing the smoky air.
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More water bombers deployed
Emergency services are using water bomber planes from Italy and France, as well as Norwegian helicopters, to try to bring the fires under control.
One water-carrying helicopter pilot, Bjorn Franzen, told the Swedish daily Aftonbladet just how difficult the mission had become.
"We fly mostly in low altitude. It's often difficult to see anything from the smoke. It can be extremely difficult to see where our input is needed. Sometimes the wind changes direction and then we need to resort to different tactics."
A German organization has also sent five helicopters with specialized equipment to help, which should arrive Saturday.
According to Swedish broadcaster SVT, Stockholm has also requested aid from Denmark and Lithuania.
'Working every minute'
Swedish Prime Minister Stefan Lofven said on Friday that his government was working "every minute" to get necessary resources to the hundreds of firefighters and emergency workers.
Some 500 voluntary soldiers from the Swedish military were dispatched to the central region of Alvdalen, while in other areas, emergency services have called for all able-bodied men to help put out the fires.
Neighboring Finland and Norway have also reported wildfires over the past few days, as Europe's Nordic region experiences an intense heatwave with temperatures over the past week reaching over 32 degrees Celsius (90 Fahrenheit).
Forecasters have warned of possible storms and stronger winds picking up over the weekend, and fanning the flames.
Dry and even hotter weather is expected after the weekend.
mm/tj (AP, dpa)