President Moon Jae-in on Wednesday ordered a probe into allegations that two senior prosecution and justice ministry officials inappropriately gave cash to prosecutors who investigated a former aide to ousted President Park Geun-hye, the presidential office said.

The rare presidential order of internal inspection follows earlier reports that a ranking ministry official with suspected links to Park's aide Woo Byung-woo treated a special probe team looking into the scandal to dinner shortly after their inquiry ended late last month. The team's leader, currently the chief of the Seoul Nambu District Prosecutors' Office, also attended the event.

At the dinner, the two senior officials offered envelopes, each containing between 700,000 won and 1 million won (US$625-$893), to each other's underlings, Yoon Young-chan, Moon's chief press secretary noted.

Woo was questioned over a range of allegations, but the prosecution's two attempts to arrest him were dismissed by a court.

The court rejection prompted suspicions that the team did not throughly investigate the case involving Woo, who once served as a senior prosecutor. 

"The internal investigation teams of the Justice Ministry and the Supreme Prosecutors' Office must thoroughly investigate the case to see if there have been any violations of the anti-graft law and make sure government officials remain disciplined," Yoon told a press briefing.

The ministry official, Ahn Tae-geun, has also been said to have held hundreds of telephone conversations with Woo while the latter was still working at the presidential office but was subject to investigation by an independent counsel.

Woo currently faces a trial over allegations that also include negligence of duty for failing to prevent Park's longtime friend Choi Soon-sil from interfering in government affairs and extorting tens of billions of won from local businesses.

He is one of very few suspects in the case to face trial without physical detention, while the former president herself remains in custody.

The justice ministry and prosecution earlier acknowledged the dinner and envelope full of what they called bonuses may have been inappropriate, but not illegal.

The money, the justice ministry has said, "was executed under related provisions for budget to partly help finance the prosecution's investigation following the end of an important case and such bonuses have been frequently given in the past."

Still, two justice ministry officials who were offered such envelopes by the chief of the Seoul Nambu District Prosecutors'

Office, Lee Young-ryeol, returned the money to the Seoul Central District Prosecutors' Office the very next day after they had dinner with Lee.

Also following the announcement of the president's order, the justice ministry released a statement, vowing to carry out a thorough inspection.

"The inspection body of the ministry will promptly establish plans in collaboration with our counterparts from the Supreme Prosecutors' Office and take the necessary measures after getting to the bottom of the case based on law and due procedures," it said. (Yonhap)