Outbreaks of the highly contagious virus are rare outside Africa, but last spring Georgia, which borders on North Ossetia, saw outbreaks in 10 regions. A total of 20,000 pigs were culled.
Some 35 animals have died in the past 24 hours of ASFV in the south Russian province, the service said.
Preliminary reports said that the infection may have been brought in by wild pigs. The virus can survive for up to 15 weeks in raw pork, and up to six months in processed meat.
The virus, which causes lethal haemorraghic disease in pigs, does not pose a threat to humans.
The area has been cordoned off, and all local pigs will be culled as a preventive measure. Around 174 people have been deployed to guard the province's border, to ensure that no pork products are taken out of North Ossetia.
At the time of the Georgian outbreak, the United Nations Food and Agriculture Organization warned of potentially severe consequences if the virus were to spread beyond the country's borders.
