Japan has banned poultry imports from North Korea because of a reported outbreak of bird flu in Pyongyang.

Earlier this week South Korea's Yonhap news agency reported that several thousand chickens died of bird flu in North Korea's capital. Yonhap says the outbreak last month prompted an emergency response from North Korean authorities. The report has not been independently verified.

Japanese officials say they imposed the ban as a preventive measure.

It is not clear what strain of the bird flu virus might be involved. A deadly strain has killed at least 34 people in Vietnam and 12 in Thailand.