One person is confirmed dead and 10 are missing after a South Korean fishing boat sank off the southeast coast early on Monday, the coastguard said.It said an air and sea search was under way for the missing after the 139-tonne vessel carrying 14 crew sank 15 miles off the coastal city of Ulsan. Three people were rescued.The boat set sail on Sunday afternoon and is thought to have sunk after suffering an engine problem in high seas.The Ulsan coastguard said it has expanded the search area with the help of other fishing boats and aircraft. The navy and air force were involved in the operation.