SOFIA, Jan 23 (Reuters) - Bulgarian authorities stepped up monitoring and testing of poultry and wild birds on Wednesday as a precaution after neighbouring Turkey found the deadly H5N1 bird flu strain in chickens.

Zheko Baichev, Bulgaria's chief veterinarian, said authorities appealed to commercial poultry farmers and owners of backyard poultry to keep chickens indoors to avoid contact with wild birds that might be infected.

Regular testing was intensified along the border with Turkey, which on Tuesday confirmed the H5N1 outbreak among chickens in a village in the northern Black Sea region.

New European Union member Bulgaria had already tightened control in its northern and north-eastern regions after the highly virulent strain was found on a small farm in neighbouring Romania in November.

Veterinary experts believe that migratory birds represent a serious risk in the spread of the deadly H5N1 strain.

The virus originated in Asia and has spread to Europe. It is known to have killed 217 people globally since 2003, according to data from the World Health Organisation.

Bulgaria, along with Romania, lie on the Pontic migratory route which wild birds use to travel from Scandinavia and Siberia to northern Africa for the winter.

Bulgaria detected the H5N1 avian flu virus in four wild swans in the spring of 2006. It has not had any outbreak among domestic fowl. (Reporting by Anna Mudeva, Editing by Peter Blackburn)

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