South Korea's Supreme Court on Thursday overturned a high court ruling that spared Samsung Group de facto leader Jay Y. Lee from jail, while it also sent a corruption case involving jailed former President Park Geun Hye back to a lower court, in a ruling that could lead to heavier sentences.

Lee, 51, heir of the country's richest family, was sentenced in August 2017 to five years in prison for bribing Park, but an appeals court in February 2018 reduced his sentence by half and suspended it for four years.

He is expected to face heavier sentencing as the top court has determined the bribery case involved a larger sum of money than what was litigated during his appeal.

Park, 67, who was impeached by lawmakers in December 2016, was sentenced by an appellate court last year to 25 years in prison over the corruption scandal that led to her ouster in March 2017, while her close friend Choi Soon Sil, 63, faces a 20-year sentence.

(Park Geun Hye)

In sending their cases back to the Seoul High Court, the top court found there had been a violation of rules for trying crimes and ordered separate trials on hercharges.

It did, however, still find Park guilty of accepting bribes from conglomerates such as Samsung and Lotte Group, determining that she had conspired with Choi in doing so.

The former president was also charged with forcing multiple South Korean conglomerates, including Samsung Group, to donate a total of 77.4 billion won to foundations under Choi's control.

(Park's Geun Hye's supporters take part in a rally held in front of the Supreme Court in Seoul to appeal for her acquittal)

Samsung, immediately after the ruling, released a statement of apology over the case, while lawyers for Samsung and for Choi called the Supreme Court's decision regrettable.

Park, who was arrested shortly after her ouster as South Korea's first female president, has criticized charges against her as political retribution and stopped appearing in court, saying she lacks trust in the judiciary.

She separately faces two years in prison for violating the public offices election law and has also been sentenced to five years in prison on embezzlement charges, but the latter case is still pending after prosecutors appealed the ruling to the top court.