SEOUL (AFP) - Under-pressure South Korean prosecutors on Monday upped to US$500,000 (S$626,485) a cash reward for information leading to the arrest of a fugitive businessman in connection with last month's ferry disaster.

The new sum was a 10-fold increase from the original amount offered last Thursday for Yoo Byung Eun, patriarch of the family that owns Chonghaejin Marine Co. Chonghaejin was the owner and operator of the 6,825-tonne ferry, Sewol, which capsized and sank on April 16 with the loss of around 300 lives - most of them schoolchildren.

Yoo is wanted for questioning on possible charges of embezzlement and criminal negligence, as prosecutors investigate the extent to which the Sewol disaster was caused by a lack of safety standards and regulatory violations.

"We hope the bigger cash reward will lead to his quick arrest," senior prosecutor Kim Hoe Jong told AFP.

Yoo has no direct stake in Chonghaejin, but his children and close aides control it through a complex web of holding companies.

His current whereabouts are unknown and a warrant was issued for his arrest after he failed to comply with a prosecutors' summons earlier this month.

Five Chonghaejin officials have already been arrested and a lesser reward of 100 million won (S$122,000) has been offered for Yoo's eldest son, Yoo Dae Gyun.

On Thursday, investigators raided a compound belonging to the Evangelical Baptist Church of Korea, of which Yoo is a leading member, but failed to find him.

Yoo has described himself as an artist and photographer and was once convicted of fraud when a company under his control went bankrupt.