SEOUL, Korea, Republic Of -- North Korea has officially confirmed the purging of its defence chief two months after Seoul's spy service said he had been executed for disloyalty to leader Kim Jong Un, a South Korean official said Monday.

South Korea's National Intelligence Service told lawmakers in May that People's Armed Forces Minister Hyon Yong Chol was killed by anti-aircraft gunfire for talking back to Kim, complaining about his policies and sleeping during a meeting.

The North's state media has since not mentioned Hyon or his disappearance. But over the weekend, the country's official Korean Central News Agency named army general Pak Yong Sik as the armed forces minister in a dispatch about a meeting with a Lao military delegation.

South Korean Unification Ministry spokesman Jeong Joon-Hee told reporters Monday that this confirmed Hyon's replacement and purging.

Since taking power upon the death of his dictator father Kim Jong Il in December 2011, Kim has orchestrated a series of executions, purgings and personnel reshuffles in what outside analysts say is an attempt to bolster his grip on power. Some experts say repeated bloody power shifts indicate the young leader is still struggling to establish himself.

South Korean officials say 70 North Korean officials have been executed since Kim's inauguration. The most notable execution before Hyon's happened in 2013 when Kim had his uncle and No. 2, Jang Song Thaek, executed for alleged treason.

Pak, known as a top official at the General Political Bureau of the Korean People's Army, is considered one of Kim's closest associates and is among the officials who have accompanied Kim on various public activities mentioned in state media.