"It is difficult to understand the special prosecution's decision," Samsung Group said in an email statement in response to the special prosecutors' decision to request an arrest warrant for Lee, the third-generation leader of South Korea's top conglomerate.

The prosecutors also said in their indictment of National Pension Service (NPS) chief Moon Hyung-pyo that he received an order from President Park Geun-hye to help the 2015 merger of Samsung C&T Corp and Cheil Industries Inc succeed.

Moon was indicted on charges of abuse of power and giving false testimony. He was arrested in December after acknowledging ordering the world's third-largest pension fund to support the $8 billion merger last year of two Samsung Group affiliates while he was head of the health ministry, which oversees the NPS.

(Reporting by Se Young Lee; Editing by Nick Macfie)