Seoul returned four North Korean fishermen and their boat Sunday after it drifted into southern waters, military authorities said, two days after Pyongyang handed back six detained South Koreans.

The vessel was picked up by a South Korean navy ship on Saturday after being spotted stranded off the country’s east coast following engine failure, officials said.

The fishermen and their boat were handed over to North Korea Sunday in an operation along the sea border, they added.

On Friday, in a move that may help relax tensions, North Korea returned six detained South Korean men across the two rivals’ heavily-militarized land border.

Border crossings between North and South are extremely rare and it is most likely that the six people returned on Friday had entered North Korea from China. (AFP)