SEOUL, May 8 Asia Pulse - A suspected case of bird flu has been reported at a farm in the upper part of South Korea, officials said Thursday, raising concerns that the deadly disease is spreading across the nation despite the government's stepped-up quarantine efforts.

The Ministry for Food, Agriculture, Forestry and Fisheries said that tests were underway to determine whether the massive death of ducks and chickens at a farm in Ansung, around 100 kilometers south of the capital, had been caused by avian influenza.

The farm reported that 502 out of 105,000 poultry it raises died on Wednesday. It is located just 4.8 kilometers away from another farm where a large number of poultry have recently died because of a highly pathogenic strain of bird flu.

Earlier in the day, tests found that the "H5" avian influenza virus was the cause of the death of poultry in Chuncheon and Busan in eastern and southeastern regions of South Korea, though further probe was needed to confirm whether the virus is highly virulent, the ministry said.

As of Thursday morning, the number of confirmed cases of highly virulent avian influenza stood at 34.

Most of the initial bird flu cases reported this year had been centered in the Jeolla region in southwestern South Korea. It has since spread to most other regions.

On Tuesday, the highly virulent strain of avian influenza was found in two dead chickens from a bird vivarium in Seoul. The outbreak in the nation's capital raised alarm that the poultry epidemic is spreading nationwide beyond control.