Choe Ryong-Hae, a member of the ruling party's politburo standing committee, was purged earlier this month, Seoul lawmakers told reporters after the National Intelligence Service (NIS) briefed them in a closed session.
Questions have swirled about the fate of Choe -- one of Kim's closest confidantes -- after his name was omitted from an official funeral committee list this month.
Kim has earned a reputation for ruthlessness after eliminating previous high-ranking officials from his ruling party.
The NIS said Choe was probably purged to take the blame for a water leak at a power station completed in late October at Mount Paekdu near the border with China.
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Choe had been chosen to take a personal message to Chinese President Xi Jinping in 2013.
Only last September he was selected to visit Beijing as North Korea's representative at China's giant World War II victory anniversary parade.
He was mentioned in state media as recently as October 31, when he made a statement about a ruling party congress to be held next year.
Rumours of political purges and even executions regularly emerge from the isolated North. Sometimes these are rebutted when the official in question resurfaces in state media.
The Kim dynasty has ruled the impoverished North for more than six decades with an iron fist and no tolerance for dissent.