North Korea has executed its army chief of staff, Ri Yong Gil, South Korea's Yonhap news agency reported on Wednesday, which, if true, would be the latest in a series of executions, purges and disappearances under its young leader. 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.