The head of Tong Yang Group was called in by prosecutors Monday over suspicions that the financially troubled group fraudulently issued commercial papers, inflicting heavy losses on retail investors.

Hyun Jae-hyun appeared at the Seoul Central District Prosecutors' Office in southern Seoul around 9:40 a.m. to undergo questioning.

The 64-year-old chairman is accused of issuing some 160 billion won ($150 million) worth of asset-backed commercial papers, a type of short-term debt, in July and September, even with prior knowledge that the firm had lost its ability to pay back its debts and was on the verge of coming under court receivership, prosecutors said.

The liquidity shortage has so far left tens of thousands of individual investors who bought the firm's bonds on the brink of losing their money, prompting a prosecution probe into alleged financial fraud.

Five affiliates of the troubled Tong Yang Group won court protection in October. (Yonhap News)