SEOUL, April 29 (Reuters) - South Korea on Tuesday reported a suspected bird flu outbreak at a chicken farm in Ulsan City, which if confirmed would be the first in the southeast, as the country grapples with its worst outbreak of avian influenza.
South Korea previously confirmed 20 cases of the H5N1 strain in poultry in less than one month, despite having killed more than 5 million chickens and ducks, as the virus spreads at its fastest rate since the country reported its first case in 2003.
No human deaths from the disease have been reported in the country.
On Tuesday, the Agriculture Ministry said a chicken farm in Ulsan, some 390 km (242 miles) southeast of Seoul, reported deaths of more than 100 chickens in a week and initial tests gave positive readings for the avian virus.
Seoul has stepped up the culling of birds in affected areas and launched an investigation into all of the country's 260 duck farms in a bid to prevent the spread of the virus.
South Korea had to kill 5.29 million birds during the first outbreak between late 2003 and early 2004. The second outbreak in 2006-2007 saw about half that number culled. (Reporting by Miyoung Kim; Editing by Ken Wills and Sanjeev Miglani)