South Korea says it will not send back nine North Korean asylum seekers who crossed the maritime border by boat nearly one week ago, despite Pyongyang's demand for their return.

The nine North Koreans were discovered late Saturday drifting in two small boats in the Yellow Sea. South Korea's Red Cross sent a message to its North Korean counterparts Friday saying all nine people have stated they want to defect, so it will handle their cases “in accordance with their free will.”

Pyongyang warned Thursday that already strained ties with Seoul would worsen if the group was not repatriated.

North Korea was angered earlier this year when the South refused to send back four citizens who accidently drifted into South Korean waters aboard a boat along with 27 other North Koreans. The four defected, but Pyongyang accused Seoul of kidnapping them.

South Korea is home to more than 21,000 North Korean defectors, largely due to political oppression and economic difficulties.

Relations between the two sides have soured in recent years, and reached a new low after two military attacks last year blamed on North Korea left 50 South Koreans dead.