Lee allegedly gave billions of won to various organizations linked to Park's confidante, Choi Soon-sil, in return for the government's backing of a controversial merger of two Samsung affiliates in July 2015. The group has acknowledged providing funds to the organizations but denied they were a bribe.

Lee was grilled by the special prosecutors for 22 hours until early Friday.

The charges under consideration include bribery, perjury and, depending on the source of the funds, embezzlement and breach of trust. 

Lee is accused of giving false testimony during a parliamentary hearing last month, during which he claimed to have "never" made donations expecting something in return.

Samsung signed a 22 billion won ($18.7 million) consulting contract in August 2015 with a Germany-based firm owned by Choi and allegedly sent the company billions of won, which was used to fund her daughter's equestrian training, according to prosecutors.

The group also donated 20.4 billion won to the Mir and K-Sports organizations, which are linked to Choi, becoming the biggest contributor to the foundations set up to promote Korean culture abroad and support local sports.

Prosecutors claimed Samsung provided the money to Choi for exerting influence to get the National Pension Service to approve the merger a month earlier, a critical step for a smooth transfer of power to the heir apparent. 

Moon Hyung-pyo, chief of the National Pension Service and former health minister, was arrested last month over his alleged role in the merger deal.

Lee Kyu-chul, spokesman for the special prosecutors' team, said there were "discrepancies in the answers required by the investigation team and the answers given by (Lee Jae-yong) on key issues."

A source close to the probe has said Lee Jae-yong, son of the ailing Samsung Group Chairman Lee Kun-hee, told prosecutors that his company was forced by Park to support Choi's businesses. (Yonhap)