Taliban insurgents stopped a bus in Afghanistan and kidnapped some of the passengers.
The Taliban said they had seized 18 Koreans - 15 men and three women.
"They are safe with us, we are investigating them, and our demands and reaction will be announced later," said Taliban spokesman.
The bus was travelling from the southern city of Kandahar to the capital Kabul yesterday when Taliban rebels stopped it.
A South Korean Foreign Ministry official said about 20 South Korean Christian volunteers were feared to have been kidnapped by Taliban insurgents.
South Korea has no combat troops in Afghanistan - only a contingent of engineers and doctors.
Taliban insurgents have kidnapped a number of foreign nationals as part of their campaign to overthrow the Afghan government and drive out its Western backers.