North Korea has admitted it is holding 21 South Koreans either captured during the 1950-53 Korean War or subsequently, the South Korean government has said.
Five Japanese also snatched by the North returned in 2002
Seoul had pressed the North about 52 POWs and 51 citizens it believes were abducted after the war.
Seoul has been raising the issue for decades, but has recently been wary of campaigning too hard for fear of damaging relations, analysts say.
It is not clear why the normally secretive North Korea has responded.
"North Korea has confirmed there are 11 abductees and 10 prisoners of war alive in the North," a South Korean Unification Ministry official told Reuters news agency on condition of anonymity.
Of the other South Koreans whom Seoul had inquired about, the North said 10 kidnapped citizens and six POWs were dead, and the rest unaccounted for.
Many people in South Korea believe around 1,000 South Koreans are alive in the North.
These include more than 540 POWs, according to the Red Cross.
A number of the kidnapped South Koreans will be able to see their families again during the next round of reunions between relatives who ended up on different sides of the Korean border after the war ended, Yonhap news agency reported. This is scheduled for 5-10 November.
Japan also believes its citizens are being held in the North against their will.
It has been much more vociferous in its inquiries, and in 2002 Pyongyang admitted it had abducted 13 Japanese citizens in the 1970s and 80s, but said eight of them had since died.
The five still alive returned to Japan three years ago, but Tokyo questions whether the others are really dead, and believes there may be yet more held captive in the North.