STOCKHOLM—One man appears to have died in Sweden's largest forest fire in more than 40 years, authorities said Tuesday, as a heat wave across several regions of northern Europe hampers firefighting efforts.

The man in his 30s was found dead on a road north of Stabäck, Västmanland. His body was badly burned, but an identity card that he was carrying matched that of a man reported missing by relatives.

The huge blaze raging in the center of the country was declared a national emergency Monday night and currently engulfs an area of 15,000 hectares northwest of Sala, about 120 kilometers northwest of Stockholm.

Some 1,000 people have been evacuated from their homes, and preparations have been made for a possible evacuation of Norberg, a town of some 4,500 people, according to information provided by Västmanland authorities.

Rescuers on Monday saved nine volunteers encircled by flames and said they would no longer accept help from private individuals because of the danger.