The chairman of embattled South Korean retail giant Lotte Group said Tuesday he is "sorry for causing concern" over corruption allegations and pledged to fully cooperate with the investigation.

Chairman Shin Dong-bin made the remark to reporters at the groundbreaking ceremony for a joint venture chemical plant in Lake Charles as prosecutors stepped up the investigation into allegations that Lotte created slush funds through illicit means.

It was the first time Shin has spoken to the media since the investigation.

"I am really sorry for causing concern over domestic issues," Shin said. "I feel responsibility and have been telling all companies to render cooperation."

Asked if the investigation is affecting his business, Shin said he hopes it will be concluded at an early date.

Prosecutors have raided a number of Lotte offices this week to seize evidence.

With the investigation, Lotte put on hold the initial public offering plan for Hotel Lotte.

The IPO plan was a key reform pledge the Lotte chairman, the second son of Lotte founder Shin Kyuk-ho, has made to improve the murky governance structure of the business empire following an acrimonious succession battle with his elder brother Dong-joo.

"This is not an indefinite postponement and I will try to do it by the end of the year," Shin said of the IPO plan. "I will make sure to have it go public as this was a promise made to the people at the National Assembly."

Shin also expressed confidence over the ongoing battle with his brother for control of the conglomerate, saying he is not concerned about it at all.

Shin said he plans to return home late this month, saying there are some things he has to take care of in the U.S. for a few weeks.

He said he will make sure to go back to South Korea after a shareholder meeting of the Lotte Holdings in Japan set for later this month. (Yonhap)