An embattled former chief of the national tax agency appeared before prosecutors Thursday to face questioning over suspicions that he took kickbacks from CJ Group in return for providing favors during a tax audit into the local food and entertainment conglomerate in 2006.

Jeon Goon-pyo, 59, arrived at the Seoul Central District Prosecutors' Office in southern Seoul around 9:40 a.m. after receiving notice of the summons earlier this week.

Jeon is under suspicion of taking US$300,000 in U.S. bills and high-end watches from CJ Group in July 2006 just after he was named the commissioner of the National Tax Service (NTS).

"I will tell everything in detail during the prosecution probe," Jeon said, when asked whether he accepts the charges brought against him.

After indicting CJ Group chairman Lee Jay-hyun of embezzlement and offshore tax evasion charges in a separate corruption case earlier this month, prosecutors have expanded their probe into the conglomerate's alleged illegal lobbying for tax breaks.

During the audit into CJ Group in 2006, tax authorities obtained evidence that the group and its chairman Lee allegedly dodged some 356 billion won (US$319 million) in corporate and income taxes. However, the NTS neither collected nor levied any fines on the family-run conglomerate.

The prosecution office suspects that CJ Group officials illegally lobbied the former top tax officials so that the conglomerate could reduce its tax burden or even avoid paying the massive amount of taxes altogether.

During prosecution questioning, CJ Group officials alleged that they gave the money and expensive designer watches to Heo Byung-ik, the NTS deputy commissioner at the time, asking him to relay them to Jeon.

Heo, who was arrested pending trial on Saturday, admitted to taking the kickbacks but claimed that he had handed the money over to Jeon, according to prosecutors.

Suspicions have also risen that Jeon, who is banned from traveling while the probe is ongoing, received the watches at a Seoul hotel as an inauguration gift from chairman Lee.

Jeon, meanwhile, has flatly denied such allegations.

"I am going to the prosecution tomorrow. I will explain everything in detail," Jeon told Yonhap News Agency on Wednesday.

It is not the first time that the former No.1 tax official has undergone a prosecution probe over similar graft allegations.

In 2011, Jeon was accused of receiving a high-priced painting from the agency's No. 2 official in exchange for securing the top post before he was officially given the job. (Yonhap News)