SEOUL, Sept. 29 (Reuters) - The missing South Korean fisheries official killed by North Korean soldiers at sea last week had expressed his willingness to defect to the soldiers, South Korea's Coast Guard said on Tuesday (Sep 29).

The official's death sparked controversy after his older brother refuted the government's initial claim that he might have tried to flee to the North.

The Coast Guard said it has determined after an investigation based on CCTV footage, military intelligence and background records that the official told the North Korean troops he wished to defect and they were aware of his detailed personal information.

"We have confirmed that the North side had secured his personal information that he would only know, including his name, age, hometown and height, and that the missing person had conveyed his willingness to go to the North," said Yoon Sung-hyun, chief of investigation and intelligence at the Coast Guard.

Yoon said the possibility was "extremely low" that he had lost his footing or attempted to take his own life because he was wearing a life vest and a flotation device when found some 38km away from where he went missing.

The man's brother, Lee Rae-jin, had said it must have been an accident as he had just got a new boat and no reason to defect.

Yoon said the official had run up debt of more than 58 million won (US$49,600) but it was still unclear whether he sought to flee because of that.

The Coast Guard and Navy have expanded the search for the man's body involving dozens of ships after Pyongyang said the soldiers only burned a flotation device he was using, in an effort to head off the risk of a novel coronanvirus outbreak.

South Korea has accused the North of dousing his body in fuel and setting it on fire after killing the man, calling for a joint investigation.

Pyongyang remains silent about the joint probe as of Tuesday but leader Kim Jong Un has offered an apology. State media said the North was conducting its own search for the man's body but warned the South against raising tension by intruding into its waters.