The presidential office on Thursday called for a thorough investigation into a senior prosecutor who has come under public scrutiny for the way he accumulated personal wealth.

Jin Kyung-joon offered to quit five days ago, when it was discovered that he pocketed millions of dollars by selling stocks of Nexon Corp., a local online game developer.

A presidential official said it's important to shed light on whether Jin may have broken the law when he bought and sold the stocks.

Another official also said Jin's resignation's offer is being held up until all suspicion is cleared. The two officials asked not to be identified, citing policy.

There is an atmosphere in Cheong Wa Dae, South Korea's presidential office, that Jin could face heavy punishment if any wrongdoing is unearthed by the probe.

Under a recent mandatory report, Jin said he sold all his

801,500 shares of Nexon listed on the Japanese stock market for about 12.6 billion won in 2015. That represented a 3.79 billion-won increase in his personal wealth from the previous year.

All ranking government officials and lawmakers are required to disclose changes in their personal wealth annually.

Jin has said he bought then-unlisted shares of Nexon in the early 2000s, saying that the investment opportunity had been initially offered to a friend of his, who then decided to share the information with many of his own friends, including Jin.

The prosecutor stressed that there was no wrongdoing involved.

Still, suspicions have arisen since Jin worked at the Korea Financial Intelligence Unit of South Korea's financial regulator, suggesting that the opportunity to purchase such large quantities of unlisted shares was possible because the company gave Jin a favor. (Yonhap)