South Korean coast guard officials work to rescue trapped Chinese crew members from capsized fishing boats in waters off Jeju Island of South Korea on Aug 28, 2012. Some 18 Chinese fishermen were rescued after two Chinese fishing boats capsized about 1.8 kilometers from Hwasun port in Jeju's Seoguipo city on Tuesday because of heavy winds and high waves unleashed by Typhoon Boleven, leaving four dead and 11 missing. [Photo/Xinhua]

SEOUL - Four Chinese fishermen are confirmed dead and eleven others are still unaccounted for after a powerful typhoon sank their fishing boats in South Korean waters early Tuesday morning.

Two fishing boats capsized around 2:40 a.m. local time in waters about 1.8 kilometers from the Hwasun port in Jeju's Seoguipo city due to heavy winds and high waves unleashed by Typhoon Boleven.

Two crew members swam ashore and reported the accident to authorities, and sixteen others were rescued later by South Korean coast guard officials. Four were found dead, putting the number of those missing at 11.

The vessels, "Yuejiangchengyu" No. 91104 and No. 91105, are both from Weihai city of East China's Shandong province.

The Jeju-based Chinese Consulate is maintaining close contact with local police in search and rescue efforts.

A typhoon alert was issued in waters off the southern resort island early Monday morning. Schools there were closed and flight services canceled.