THE driver of a South Korean businessman wanted over the sinking of a ferry that killed 304 people has turned himself in, potentially unlocking the mystery of his boss's final days.

Prosecutors in Incheon said Yang Hoe-jung turned himself in at their office, which is investigating the role of businessman Yoo Byung-un in the sinking of the ferry Sewol.

Mr Yoo's body was found by a farmer in an orchard on June 12.

The structurally defective and heavily overloaded ferry capsized and sank on a routine journey on April 16, killing 304 people, 250 of them teenagers from the same school on a class field trip. Twelve of their teachers also died in the incident, the country's worst maritime disaster in 44 years.

The driver was the last among a group of people close to Mr Yoo who had been wanted for allegedly helping him elude South Korea's biggest manhunt.