Prosecutors investigating the fatal sinking of a South Korean ferry have raided the home of Yoo Byung-un, the head of a family that owns the Chonghaejin Marine Company and its ferry.

Kim Hoe-jong, a prosecutor on the case, said Wednesday's raid was part of a probe into "overall corruption in management."

Of the 476 passengers and crew on board the Sewol, 339 were children and teachers on a high school outing to the holiday island of Jeju. Only 174 people have been rescued and the remainder are presumed to have drowned.

The confirmed death toll rose to 159 Wednesday, said broadcaster KBS.

South Korean prosecutors and agencies tend to adopt a blanket approach in raids, rather than targeting specific lines of inquiry.

They raided the home of one of Yoo's sons on Wednesday, but found that he was away and the door was locked and they could not enter the house. They also raided an office in the premises of a branch of a church that Yoo founded.

Financial regulators are also investigating whether the wider conglomerate group illegally used overseas borrowings.

Reuters