A passenger ship carrying some 350 on board was sinking in waters off South Korea's southwest coast on Wednesday morning, Xinhua news agency reports.

South Korea's Yonhap news agency puts the number of people on board at around 450.

The ship "SEWOL," departed from South Korea's Incheon for Jeju, was flooded with sea water and inclined over 20 degrees. Passengers are now waiting for rescue on the leaning ship, according to local TV station YTN.

Most of the passengers are high school students on the way to Jeju Island on a school trip, Yonhap reports.

The South Korean Coast Guard said it dispatched patrol boats and aircraft to the scene for rescue operations.