The late Yoon, formerly a professor emeritus at Yonsei University, had been hospitalised for an unspecified illness and died shortly after the president delivered a speech marking the anniversary of Korea’s liberation from Japan’s 1910-45 colonial rule.

“The president went to the hospital after the Liberation Day ceremony this morning, and stayed by his father’s side when he passed away,” Yoon’s office said in a statement.

Yoon was scheduled to depart on Thursday for the first-ever standalone trilateral summit with US president Joe Biden and Japanese prime minister Fumio Kishida at Camp David in Maryland, where they will launch a series of joint initiatives on technology, education and defence, senior US officials said.

Yoon’s office said he has decided to hold a private funeral with only family members so that there would be “no vacuum in state affairs,” without elaborating.

In South Korea, the oldest son plays a major role in family funerals, which usually last three days but could go longer in some cases. Yoon has a younger sister.

A prominent economist, the late Yoon gained fame for his research on South Korea’s inequality and economic growth using statistical methods.