Lithuania on Thursday destroyed thousands of pigs after confirming its first cases of deadly African swine fever, days after it was detected on farms in EU neighbours Latvia and Poland.

The spread of the disease, which is harmless to humans but poses a grave threat to pigs and the pork industry, comes as the World Trade Organization reviews a Russian embargo on EU pork sparked by the outbreak.

Lithuania's state food and veterinary service said cases were reported in the north-east of the country, close to Latvia and Belarus, on an industrial-scale farm owned by Danish company Idavang.

"The farm had around 19,000 pigs, and they are being destroyed," Idavang spokeswoman Lina Mockute told AFP.

The developments come the day after Lithuania's southern neighbour Poland suffered its first cases of swine fever in pigs, and two days after northern neighbour Latvia extended an emergency zone for the same reason. Poland on Wednesday confirmed its first cases of deadly swine fever in domestic pigs, as the World Trade Organisation reviewed a Russian embargo on EU pork imports imposed over the disease.

Russia in January imposed a pork embargo on the 28-nation European Union but Brussels turned to the World Trade Organization, arguing the ban is totally misplaced.

WTO's disputes settlement body have created panels to hear the complaint, trade sources said earlier this week.

Russia buys a quarter of the EU's pork exports, worth around 1.4 billion euros ($1.9 billion) a year.

Lithuania ordered a mass cull of wild boar earlier this year, targeting 90 percent of the estimated 60,000 living on its territory, after the disease was detected in animals thought to have come from Belarus.