The bird flu outbreak that has swept South Korea reached the capital Seoul on Tuesday, prompting quarantine officials to decontaminate and limit access to a nearby children's park and open air market.

The Ministry for Food, Agriculture, Forestry and Fisheries said tests conducted on four birds that started dying off from late April showed they were contaminated with the H5 avian influenza virus.

The bird vivarium located at the Gwangjin ward office in eastern Seoul raised 57 chickens, ducks, pheasants and turkeys. The outbreak marks the first time that the avian influenza has hit Seoul since quarantine officials received reports of wholescale bird deaths on April 1.

The ministry said all birds in the vivarium have been culled and buried as a precautionary measure, while detailed tests to determine if the deaths were caused by a virulent strain of the bird flu will be made known later in the day.

"Interviews with the ward's workers revealed that the pheasant that died on April 28 was bought at a livestock market in Seongnam, south of Seoul," a quarantine official said. He added that inspectors have been dispatched to the market to check for additional contamination and to find out how the pheasant got sick.

The expert said while there was little chance of the bird flu spreading in an urban environment, authorities have sealed off Children's Grand Park located 1.2 kilometers from the vivarium and Gyeongdong market, where some live poultry transactions take place.

Most of the initial bird flu cases reported this year were centered in the Jeolla region in southwestern South Korea. It has since spread through most of the country with bird deaths being reported in Gyeongsang region in the southeast and two cities in Gyeonggi Province south of Seoul.