A Chinese fishing boat capsized off South Korea's southwestern Gageo Island on Sunday, leaving three crew members missing and two others in cardiac arrest, Coast Guard officials said.

The 98-ton vessel sank in international waters about 80 kilometers off Gageo Island, according to officials.

Of the 11 people on board, six were initially rescued by another Chinese vessel operating nearby. The Coast Guard later rescued two more who were drifting at sea, but both were found in cardiac arrest and rushed to a hospital, officials said.

The Coast Guard said a search operation is under way for the three missing fishermen in cooperation with its Chinese counterpart.