Russia has reported an outbreak of highly pathogenic H5N2 bird flu on a farm in the central region of Kostromskaya Oblast that led to the deaths of more than 660,000 birds, the Paris-based World Organization for Animal Health (OIE) said Friday.

The virus killed more than 44,000 birds in an outbreak first detected on December 17, the OIE said, citing a report from the Russian Ministry of Agriculture.

The rest of the 663,500 birds on the farm were slaughtered, it said in the report. It did not specify the type of birds that were infected.

It is the first outbreak of the H5N2 strain in Russia this year, but the country has been facing regular outbreaks of H5N8 since early December last year, with the last one reported to the OIE detected late November.

Bird flu has led to the deaths or culling of more than 2.6 million birds on farms between December last year and November this year, a report posted on the OIE website showed.

Neither the H5N2 or H5N8 strains has been found in humans.

The virulence of highly pathogenic bird flu viruses has prompted countries to bar poultry imports from infected countries in earlier outbreaks.