A fishing boat carrying 31 North Koreans has drifted across a tense border near a South Korean island shelled by the North last year, local media reported on Monday.
The North Korean boat, with 11 men and 20 women on board, was spotted near Yeonpyeong island and towed to the western port city of Incheon, Yonhap news agency said. The North Koreans are currently being questioned, it said.
So far, the North Koreans have not expressed a wish to defect, a military official was quoted as saying by Yonhap.
Another military official said the boat was spotted in thick fog by the South's military stationed on the island, which is 11 km (7 miles) from North Korea's shores, Yonhap reported.
Government officials refused to comment on the reports.
The case comes as military officials from the two Koreas ready for talks Tuesday, the first dialogue between the rivals since the North's deadly attack against Yeonpyeong last November.
Colonels from the two countries will meet at a truce village on their heavily fortified border in a test of a pledge by the North to ease tensions.
South Korea accused the North last March of torpedoing one of its navy ships, killing 46 sailors. Pyongyang denied it sank the vessel.
In November, the North bombarded Yeonpyeong island in disputed waters off the west coast, killing four people including two civilians. The North said it was provoked into the attack by a South Korean artillery drill in the area.
Tuesday's preliminary round of military talks will set the time and agenda for higher-level talks, possibly between defence ministers.
Regional powers have nudged the rivals to defuse the crisis and restart international talks over the North's nuclear program. The two Koreas are still technically at war because an armistice, not a treaty, ended the 1950-53 Korean War.