The Swedish Civil Contingencies Agency (MSB) said two Italian firefighting aircraft had been sent to assist in badly hit areas of central Sweden, while Norway had dispatched six helicopters.
Norway has suffered from considerable forest fires of its own over the last week, with wildfires in 100 locations in the south last week, some of which were triggered by lightning.
One Norwegian firefighter lost his life responding to the blazes while the country's Home Guard has also been deployed to relieve strained fire services.
But the many forest fires that raged across southern Norway in recent days, particularly on Saturday and Sunday, are now under control or completely extinguished, news agency NTB reported on Wednesday.
Despite that, the Home Guard is still assisting fire services in some areas, VG reports.
MSB said it had asked the EU Civil Protection Mechanism for more firefighting planes in addition to those sent from Italy due to lack of capacity and manpower in Sweden.
"The drought has led to a large amount of simultaneous fires in the forests and land," emergency services company SOS Alarm said in a statement, adding that the number of fires would "likely" increase on Wednesday.
"This is not looking good, it's burning uncontrollably and spreading quickly," rescue officer Torbjorn Wannqvist told TT.
Swedish authorities said 44 fires were burning across the country on Wednesday, urging locals living close to the blazes in the central counties of Gävleborg, Jämtland and Dalarna to evacuate.
Even northern Swedish Lapland, inside the Arctic Circle, has been affected.
Five wildfires were burning Wednesday in the forests outside the town of Jokkmokk, a popular tourist destination in the winter.
"The last time we saw wildfires of this calibre was 12 years ago," Jokkmokk rescue officer Thomas Andersson told AFP.
MSB fire chief Britta Ramberg told TT news agency the fire in Jämtland was "the largest and spreading the fastest".
The fire there had already engulfed 2,500 hectares (6,000 acres) and was spreading by 10 square metres (100 square feet) a minute, authorities said.
No casualties have been reported so far from the Swedish fires.
Meteorologists have in recent days warned of extremely hot temperatures in Sweden, saying it's "unusual" for a heatwave to last this long.