South Korean prosecutors raided the offices of Samsung Group on Wednesday, a prosecution official said, after media reports of alleged links with a confidante of President Park Geun-hye who has been indicted in a scandal.

Prosecutors also raided South Korea's largest pension fund, the National Pension Service (NPS), an NPS spokeswoman said. The Yonhap news agency reported that investigators were probing NPS's decision to approve the $8 billion merger of Samsung C&T Corp and Cheil Industries last year.

Korean prosecutors are expanding their investigation into allegations of influence-peddling in the corruption scandal that has rocked Park's presidency over the relationship between the government and big businesses.

NPS, the world's third-largest pension fund, has come under scrutiny by the media and civic groups over its approval as a major shareholder of the merger between two affiliates of Samsung Group, South Korea's largest family-run conglomerate.

A Samsung Group spokeswoman confirmed prosecution officials had visited the group's headquarters.

Park and her confidante, Choi Soon-sil, are under investigation for allegedly improperly pressuring major conglomerates, including the Samsung Group, to raise funds for foundations that backed Park's policy of promoting the cultural and sports communities.