ABUJA (Reuters) - Infected migratory birds from Europe or Central Asia were probably to blame for spreading a new strain of H5N1bird flu to Africa, Nigeria's chief bird flu expert said on Tuesday.

The United Nations Food and Agriculture Organization reported on Monday that the strain of avian influenza recently found in Nigeria was genetically different from the strains in previous African outbreaks.

Mohammed Saidu, head of Nigeria's bird flu control program, said the H5N1 strain was discovered last month in a duck at a poultry market in northeast Gombe state.

"Since that location is among the 24 wetlands we have in Nigeria and along the two migratory routes, we suspect that the strain could have come from the migratory birds," Saidu said.

A senior FAO official on Monday expressed doubts that wild birds carried the strain to Africa since this year's southerly migration has yet to begin.

Scott Newman, International Wildlife Coordinator of FAO's Animal Health Service, said the virus may have instead reached the continent via international trade.

In late July, Africa's most populous country discovered its first cases of H5N1 bird flu virus in almost 10 months. The virus, which can spread to humans, was found in poultry markets in the northern cities of Kano and Katsina.

Avian influenza is common, but the H5N1 strain is particularly worrying both to poultry producers and doctors.

It rarely infects people but has killed 243 out of 385 known to have been infected since 2003, according to the World Health Organization. It has killed or forced the slaughter of 300 million birds.

(Writing by Randy Fabi; Editing by Tume Ahemba)