General Ri Yong-Gil, chief of the General Staff of the Korean People's Army, was killed last week after being accused of corruption and other charges of pursuing personal gains, sources told the Yonhap agency.
"Ri Yong-Gil is known to have been faithful to principles, so it appears the North cited (the charges) to justify his execution," one source said.
The general was put to death around the time Kim was chairing a joint meeting of the North's ruling Workers' Party and the military, they said.