The news comes amid heightened tension surrounding isolated North Korea after its Sunday launch of a long-range rocket, which came about a month after it drew international condemnation for conducting its fourth nuclear test.
A source familiar with North Korean affairs also told Reuters that Ri had been executed. The source declined to be identified, given the sensitivity of the matter.
Ri, who was chief of the Korean People’s Army (KPA) General Staff, was executed this month for corruption and factional conspiracy, Yonhap and other South Korean media reported.
Yonhap did not identify its sources. The source who told Reuters the news declined to comment on how the information about the execution had been obtained.
South Korea’s National Intelligence Service declined to comment and it was not possible to independently verify the report.
The North rarely issues public announcement related to purges or executions of high-level officials.
A rare official confirmation of a high-profile execution came after Jang Song Thaek, leader Kim Jong Un’s uncle and the man who was once considered the second most powerful figure in the country, was executed for corruption in 2013.
In May last year, the North executed its defense chief by anti-aircraft gun at a firing range, the South’s spy agency said in a report to members of parliament.
The North’s military leadership has been in a state of perpetual reshuffle since Kim Jong Un took power after the death of his father in 2011. He has changed his armed forces chief several times since then.
Some other high-ranking officials in the North have been absent from public view for extended periods, fuelling speculation they may have been purged or removed, only to resurface.