South Korea has refused to hand over two North Koreans found on a small wooden boat in southern waters, in a development expected to draw an angry response from the North.
The two North Korean men were spotted by South Korea's navy just south of the Koreas' eastern sea border earlier this week, and Pyongyang has demanded their return.
More than 21,000 North Koreans have fled to South Korea since the end of the 1950-53 Korean War, with defections surging in recent years amid economic hardship in the North.
Defections are a sore point in relations between the divided Koreas; South Korea accepts those who choose to defect and repatriates those who wish to return home.
But the North often claims that its citizens are held against their will in the South and that South Korean officials pressure them to defect.
South Korea's Red Cross sent a message saying that the two North Koreans want to defect, and that Seoul will honour their wishes, according to Seoul's Unification Ministry.
North Korea did not immediately respond, but it angrily warned earlier this year that ties would suffer after South Korea rejected its repatriation demands for some of its citizens who had crossed into South Korean waters aboard boats.
On Tuesday, nine other North Koreans arrived in South Korea about three weeks after they were found on a wooden boat off the coast of Japan. Tokyo decided to honour their wishes to be sent to South Korea.
The latest defections come as animosities between the Koreas ease. Diplomats from the rivals have held talks aimed at resuming stalled international negotiations on the North's nuclear programme.
The Koreas' ties badly frayed last year because of two attacks blamed on Pyongyang that killed 50 South Koreans.