SEOUL -- South Korean prosecutors on Sunday summoned Lee Jae-yong, Samsung Electronics' vice chairman, for questioning over a scandal involving President Park Geun-hye's longtime confidante, Yonhap news agency reported.

Lee was summoned in the afternoon by the Seoul Central District Prosecutors' Office in charge of investigation into the scandal of Choi Soon-sil suspected of using her close friendship with the president to win personal gains.

Choi, whose friendship with Park dates back to the mid-1970s, has been arrested for abuse of power and attempted fraud. The 60-year-old is alleged to have pressured big companies into donating 77.4 billion won ($66.3 million) to two nonprofit foundations presumably controlled by Choi.

President Park held an open meeting with 17 chiefs of the country's conglomerates on July 24, and had closed-door meetings, separately one by one, with seven of them until the following day.

The Samsung vice chairman is being grilled by prosecutors over the closed-door meeting and why Samsung made the biggest donation of 20.4 billion won to the Choi-controlled foundations.

Lee has actually run Samsung Group, South Korea's largest family-run conglomerate, since his father Lee Kun-hee, chairman of Samsung Electronics, was hospitalized for heart attack in 2014.

Prosecutors also reportedly questioned Lee about why Samsung transferred 28 billion euros (about $30 billion) last year to a company in Germany co-owned by Choi and her 20-year-old daughter.

Samsung in charge of the Korea Equestrian Federation claims that it was sent to support six horse riders, but the money was spent solely on Choi's daughter who was previously a member of the national equestrian team.