July 28 (Bloomberg) -- Nigeria, Africa's most-populous nation, reported new outbreaks of bird flu in two of its northern states, the World Organization for Animal Health said.

Both cases, confirmed to be the H5N1 strain of avian influenza, occurred in ``backyard poultry'' in Kano and Katsina states, the organization said a statement posted on its Web site on July 25.

``Detailed investigation is ongoing, but information so far indicates the introduction of new species into existing flock as possible cause of the outbreak,'' the organization said. More than 5,000 birds from the two farms, including chickens, ducks and guinea-fowls, have been destroyed to prevent further spread of the virus, it added.

The H5N1 strain of bird flu has spread to more than 60 countries and has killed 243 people in 12 countries as of June 19, according to the World Health Organization's Web site.

Junaid Maina, head of the livestock in Nigeria's Agriculture Ministry, didn't answer calls to his mobile phone seeking coment.

To contact the reporter on this story: Dulue Mbachu in Lagos via Johannesburg at pmrichardson@bloomberg.net.

Last Updated: July 28, 2008 12:15 EDT