SEOUL - A South Korean independent counsel team investigating a scandal involving impeached President Park Geun-hye on Monday summoned two key Samsung Group executives for bribery charges.

Choi Ji-sung, head of Samsung Group's future strategy office, appeared in the special prosecutor team's office in the southern district of Seoul, local TV footage showed.

Chang Choong-ki, the office's vice head, was also summoned for his suspected involvement in the presidential scandal.

They were summoned as reference witnesses, but their legal identities can be changed into criminal suspects after interrogation, the team's vice spokesman said in a text message.

Choi, who has the title of vice chairman, is considered as the group's Number 2 man under the leadership of Samsung Electronics Vice Chairman Lee Jae-yong, an heir apparent to Chairman Lee Kun-hee who has been hospitalized for over two and a half years for heart attack.

The office, which is a de-facto control tower of South Korea's largest family-run conglomerate, is suspected of having been involved in bribing the impeached president and her longtime confidante, Choi Soon-sil, in return for getting favors in the group's all-important merger in July 2015 of two Samsung affiliates.

The merger between Samsung C&T and Cheil Industries was extremely crucial to Vice Chairman Lee as it is aimed at creating the group's de-facto holding company to transfer management control from Lee to his only son, the younger Lee.

South Korea's national pension fund approved the merger despite strong opposition from foreign shareholders for an unfair exchange ratio. The National Pension Service (NPS) was the biggest shareholder of Samsung C&T at the time.

President Park is suspected of ordering former welfare and health minister, who has been in custody, to pressure the NPS into approving the Samsung merger.

Samsung provided millions of US dollars to support the equestrian training of the daughter of Chio Soon-sil, Park's decades-long friend, while making the biggest donations to two nonprofit foundations presumably controlled by Choi.

The conglomerate also donated millions of dollars to a winter sports center presumably controlled by Choi and her niece.