A Seoul court on Wednesday sentenced a former manager of Kookmin Bank's unit in Tokyo to six years behind bars for extending illegal loans worth nearly 350 billion won ($317 million) to South Korean companies operating in Japan.

The Seoul Central District Court also imposed a 90 million won fine and an additional 90 million penalty on the 56-year-old former manager of South Korea's leading bank's Tokyo branch, only identified by his surname Lee, for playing a leading role in granting unauthorized loans between January 2007 and January 2010.

The Tokyo branch was scrutinized earlier this year after allegations rose that it lent more than permitted to Japan-based firms to secure returns, some of which were later used to amass slush funds here.

In the same ruling, the court handed down a four-year prison term to another employee, surnamed Ahn, for colluding with Lee.

"The two granted unauthorized loans while working as a manager and a co-manager of the Tokyo branch," Judge Cho Yong-hyeon said in his ruling, adding that their crime incurred huge losses to the lender.

The two were convicted of forging loan application documents and overvaluing collateral in order to grant massive loans to business groups. (Yonhap)