Seven workers at a poultry plant in southern Russia have been infected with a bird flu virus, according to Russian News Agency TASS.

TASS reported on Saturday (local time) that Russia had registered the cases, quoting public health official Anna Popova, the head of Rospotrebnadzor, a consumer health watchdog.

It appears to be the country's first case of bird flu being passed to humans from birds, but there is no sign of transmission between humans so far, Popova was quoted as saying.

Russia has reported the case to the World Health Organization, she added.

The strain of bird flu virus is reported as A(H5N8), a strain that has also been detected in Europe, China, North Africa and the Middle East in recent months, but only in poultry.

It's understood the seven workers became infected in December and have since recovered.