A dead wild boar in Sweden has tested positive for African swine fever, Reuters reported, citing Sweden's Veterinary Institute on Wednesday, the first such case in the country.

African swine fever is harmless to humans but is highly contagious and deadly in domestic pigs and wild boars. It has spread from Africa to Europe and Asia and has already killed hundreds of millions of pigs, affecting global meat markets.

Seven dead boars were found in Fagersta, some 200 kilometers (124 miles) north-west of Stockholm, and more tests are being conducted, the Veterinary Institute said in a statement.

"At present, we do not know how the infection got in, but it is a long jump from the nearest infected area in Europe, and we therefore assume that it has happened through humans and not wild boar," it said.

While the virus does not affect humans or other animals, it can be spread via pork or by carrying it on shoes, tools or vehicles.

An outbreak of African swine fever has forced pig breeders in Serbia, Bosnia and Croatia to cull thousands of pigs since June and is putting pressure on governments to compensate farmers for their losses.