A former close aide to President Lee Myung-bak was grilled in a marathon interrogation until early Saturday over his suspected bribery from a savings bank chief at the center of a lobbying scandal, prosecutors said.

Kim Hee-jung, a former secretary who handled the president's personal affairs, appeared before prosecutors on Friday to face questioning on suspicions of receiving around 100 million won ($87,657) in kickbacks from the now-jailed Solomon Savings Bank's Chairman Lim Suk, who is accused of a massive lobbying campaign to prevent the ailing bank from being shut down.

Asked whether he admitted to the bribery allegations after nearly 15 hours of interrogation, Kim simply said he "sincerely responded to the questions."

Having secured evidence of the suspected bribe taking, prosecutors questioned him over whether the kickbacks were in exchange for peddling influence on behalf of the savings bank, according to prosecution sources. But Kim denied most of the allegations during the interrogation, they said.

Kim, however, was remorseful for the negative light the allegations have brought to President Lee.

"I caused irrevocable, huge trouble to the president. I will spend the rest of my life offering an apology," he said.

The prosecution said it will decide whether to seek an arrest warrant after thoroughly reviewing the interrogation results.

The long-time aide had worked for Lee since 1997 when the president was a lawmaker. He resigned from the secretary post earlier this week after local media raised the allegations against him. Kim has maintained his innocence, but said he wanted to practice "moral responsibility." (Yonhap)