Ji Seong-ho made the comment without citing his source, according to South Korea’s Yonhap News Agency. Rumors have swirled in recent weeks over Kim’s health after the dictator was last spotted in public April 11.
"I've wondered how long he could have endured after cardiovascular surgery. I've been informed that Kim died last weekend," Ji told Yonhap.
"It is not 100 percent certain, but I can say the possibility is 99 percent,” he added, speculating that North Korea, which “is believed to be grappling with a complicated succession issue,” may officially announce the news this weekend.
But recent satellite photos indicate Kim Jong Un might actually be hunkering down at a luxury coastal resort on the Hermit Kingdom's northeast coast.
A key aide to the president of South Korea also insisted on Sunday that Kim, who is believed to be 36, was "alive and well."
"He has been staying in the Wonsan area since April 13," Chung-in Moon, foreign policy adviser to South Korean President Moon Jae-in, told Fox News. "No suspicious movements have so far been detected."
An intelligence source told Fox News Monday there have been suspicions that Kim has been unwell since April 15.
Speculation about Kim's health has been running rampant since he missed an April 15 commemoration that celebrated the 108th birthday of his late grandfather, North Korea founder Kim Il Sung. He was last seen on April 11.
Fox News’ Travis Fedschun contributed to this report.