SUNGNAM, July 27: More than 200 North Korean refugees flew into South Korea on Tuesday, arriving in a secretive operation aboard a specially chartered plane from an unidentified Southeast Asian country.

The first of two planes carrying the refugees - the biggest single batch ever - touched down at a heavily guarded military airport in Sungnam, south of Seoul, said a Reuters photographer at the scene.

Groups of people disembarked to be met by officials and were quickly driven away in a convoy of six buses to an unknown destination. "We believe there are about 230 people arriving today," said Chun Ki-won, who heads a group of missionaries helping North Korean defectors. "We expect about the same number tomorrow."

The South Korean government, which has been working behind the scenes to bring the refugees to Seoul, has been tight lipped about the process and declined to confirm where the chartered Asian a Airlines plane had come from, or who was on board.

However, sources in Vietnam said North Korean refugees had been gathering in southern Ho Chi Minh City, formerly Saigon, after trickling over the border from China for months.

South Korea's Yonhap news agency quoted government sources as saying the sheer number of refugees who were crammed into safe houses and their long wait drove many of the refugees to threaten suicide unless their cases were resolved.

The threats prompted Seoul to intervene officially in May and ask the country to allow "every one of them" to go to the South, Yonhap said. Sources in South Korea said the backlog accounted for more than one year of refugee arrivals in the country. -Reuters