The highly contagious disease, which is incurable in pigs but harmless to humans, has spread rapidly across the northern part of Bulgaria, reports Reuters.
The Black Sea state has reported more than 30 cases of African swine fever in several regions, including border provinces with Romania, in July 2019.
Bulgaria found three new cases of the disease in dead wild boar in separate regions of northern Bulgaria on Wednesday, as well as one case among backyard pigs in the town of Targovishte in the north east of the country, the food safety agency said.
All pigs within a 3-kilometre quarantine zone established around the Targovishte backyard will be culled, the agency said in a statement.
"The pig-breeding is a competitive 600-million levs industry, which covers 40 percent of the domestic consumption of pork," Agriculture Minister Desislava Taneva, who announced several protective measures on African swine fever, told a news conference.
Taneva said forestry enterprises will pay 150 levs for each wild boar killed as the Bulgarian authorities are aiming to reduce significantly the wild boar population density in 20km zones around the African swine fever outbreaks.
The head of Bulgaria's food safety agency Damyan Iliev said last week the damage the country could sustain if it fails to cope with the disease could total as high as 2 billion levs.
Preventative measures also include enhancing traffic control in these areas and border points with the help of police and the army, disinfecting farms and restricting sales of pork and processed meat, Taneva said.
The Bulgarian government last week granted 3.7 million levs to combat African swine fever in the Balkan country with 1.2 million farm-raised pigs.
Bulgaria's food safety agency turned to farmers in the country on several occasions, saying it is essential for them to comply with the rules on disease prevention, and all sick and dead pigs should be reported immediately.