The former head of Woori Bank's Tokyo branch under investigation for suspected involvement in illegal lending was found dead Tuesday, sources said.

The senior official, only identified by his surname Kim, was found dead after apparently committing suicide, sources said.

The financial regulator is probing Tokyo branches of Woori Bank and state-run Industrial Bank of Korea on suspicion of creating slush funds following similar irregularities at Kookmin Bank's Tokyo branch.

The Japanese branch of Kookmin, Korea's leading bank, has been under investigation on suspicion of extending about 400 billion won

($376.9 million) worth of illegal loans to Japan-based firms to secure returns, some of which were later used to amass slush funds in Korea.

Woori Bank reported to the financial watchdog that suspected illegal lending is estimated to have reached around 60 billion won. (Yonhap)