Seoul's Defense Minister Yoon Kwang-ung says some 542 South Korean prisoners-of-war (POW) are believed to remain alive in North Korea as of the end last year.

Yoon made the comments in response to lawmakers' questioning during an interpellation session at the National Assembly on Monday.

He said a total 1,523 former South Korean soldiers had not been returned to the South in the aftermath of the Korean War, out of which only a fraction is estimated to have survived.

Yoon also said Seoul had brought up the issue during high-level military talks between South and North Korea in 2000, but was stonewalled by North Korean officials who said no such prisoners existed in the North after the prisoner exchange that took place in 1954.