According to reports by Reuters, almost 130,000 pigs have been killed on six breeding farms in the Black Sea country in the past two weeks. Authorities have so far detected 30 incidents of African swine fever (ASF) at industrial or backyard farms.

In an attempt to stop the spread of the virus, the Agriculture Ministry has set up 20km (12.4 miles) sanitary zones around all registered industrial pig farms in the country, with officials ordering the culling of home-raised pigs in these zones.

Borissov said the government would pay 300 levs ($170) to every owner who voluntarily culled their pigs, adding that 75 percent of the sum will be provided by the European Union.

His announcement came after protests in several parts of southern Bulgaria on Friday, with hundreds resisting government orders to kill their pigs or face the animals being culled by the Food Safety Agency, saying there had been no swine fever outbreaks in their regions.

"No one is pleased about this," Borissov said late on Friday (2 August) in the southern town of Pazardzhik. "It is like protesting against cancer. We managed to master it for two years, but now we are not."

Bulgaria is one of the poorest European Union member states and almost every household in rural areas keeps home-raised pigs. Industry officials fear the virus could cause damages of up to 2 billion levs ($1.1 billion).

Analysts say the price of pork in the country has increased by up to 30 percent in less than a month because of the outbreaks and could rise by a further 15 percent in the autumn.