SEOUL (AFP) - The head of South Korea's KT Corp - the top fixed-line phone operator and number two mobile carrier - has offered to resign following a corruption probe, a report said on Sunday.

Chairman Lee Suk Chae has told his board of directors that he would step down, Yonhap news agency reported.

On Friday state prosecutors raided the offices of KT and the homes of its executives.

The probe focuses on breach of trust charges filed against Lee, alleging the existence of a slush fund and poor investment decisions that cost the firm hundreds of millions of dollars.

Lee, a confidant of former president Lee Myung Bak, has rejected the allegations as "groundless".

KT's third-quarter net profit plunged 63 percent from a year earlier to 136 billion won (S$158 million).