Latvia on Tuesday declared a state of emergency in a second area of this Baltic EU state as efforts continued to contain an outbreak of deadly African swine fever in its pig population.

The extension of the emergency quarantine zone means large swathes of Latvia's borders with Belarus, Estonia, Lithuania and Russia now fall within it.

Inside the zone, animals cannot be moved between farms, access is restricted to infected farms and inspectors can order culls on the spot.

The government also approved measures Tuesday including compensation for small farmers who have had to slaughter diseased pigs and broader rights for veterinary inspectors in accessing private property.

Prime Minister Laimdota Straujuma warned Tuesday of "major losses" to the farming sector unless the disease is contained, with Russia and Belarus already slapping blanket bans on Latvian pork products.

Straujuma blamed wild boar crossing in from Russia for Latvia's first-ever outbreak of the disease, detected on June 26.

Since then, a total of 26 wild boar and 19 pigs on 11 farms have tested positive for it, and 185 pigs have been put down.

Experts believe it first emanated from Belarus, and was also confirmed earlier this year in wild boar in fellow European Union members Poland and Lithuania.

The disease is harmless to humans but lethal to pigs and has no known cure.

Posing a lethal threat to commercial pig farms, African swine fever has spread throughout the Balkans, the Caucasus and Russia since 2007, and is endemic to areas of Africa, according to the United Nations' Food and Agriculture Organisation (FAO).

The FAO warns of "vast losses" if it migrates from Russia to China, which is home to half of the world's pigs.