President Yoon Suk Yeol on Thursday offered his condolences over the death of a Marine who was swept away by a torrent during search and rescue operations for victims of recent downpours.

"I express my sincere condolences over L. Cpl. Chae Su-geun's death in the line of duty," Yoon said in a message relayed by presidential spokesperson Lee Do-woon.

"The government will thoroughly investigate the cause of the accident to ensure such incidents do not recur," he said.

Yoon promised the government will treat the lance corporal with the utmost respect as a person of national merit.

Chae disappeared into the Naeseong stream rapids in Yecheon County, 161 kilometers southeast of Seoul, on Wednesday, a day after he was deployed for the search operations, according to the Marine Corps.

Rescue authorities discovered his body late at night, some 5.8 kilometers downstream from where he first went missing.

Public criticism arose as troops mobilized for the operations at the stream searched for victims without wearing life vests. (Yonhap)