North Korea has promoted Gen. Ri Myong-su, chief of the military's general staff, to vice marshal, the North's media said Friday, a move designed to help its leader tighten his grip on power.

The 82-year-old Ri, chief of the General Staff of the Korean People's Army, was bestowed with the title on Thursday, a joint decision made by the North's key military commissions, the Korean Central News Agency said.

Early this year, Gen. Ri was promoted to the chief of the KPA's general staff to replace his predecessor Ri Yong-gil, who is believed to have been executed on corruption charges.

North Korea's military has special general officer ranks -- marshal and vice marshal. Its general officer ranks have four titles -- general, colonel general, lieutenant general and major general.

The KCNA also said that two KPA commanding officers -- Kim Yong-chun, 80, and Hyon Chol-hae, 82 -- were given the title of marshal.

The report said that they have made great contributions to thoroughly establish the party's monolithic command system in the KPA and strengthen the military by remaining faithful to the leadership.

Since Ri Ul-sol, the last remaining marshal of the KPA, died in November last year, the North has only had the marshal of the Democratic People's Republic of Korea -- its leader Kim Jong-un.

The two newly-appointed marshals were key military aides to Kim Jong-il, the father of the current leader who died in December 2011, experts say.

Vice marshal Ri is viewed as spearheading efforts to boost the military's monolithic command scheme, earning trust from North Korean leader Kim Jong-un, according to Yang Moo-jin, a professor at the University of North Korean Studies.

"The promotion appears to be aimed at succeeding the spirit of revolutionary fights and beefing up the current leader's grip on power," said Yang Moo-jin, a professor at the University of North Korean Studies.

The lineup came on the occasion of North Korea's celebration of the 104th birthday of North Korea's late founding father Kim Il-sung.

Earlier in the day, North Korea attempted to launch what appeared to be the Musudan medium-range ballistic missile, but the launch seems to have ended in failure, the South Korean Joint Chiefs of Staff said.

If confirmed, it was the North's first test-launch of the Musudan missile which is believed to be capable of flying as far as Guam with a range of 3,000-4,000 kilometers.

The launch came amid high speculation that North Korea may carry out its fifth nuclear test or fire off a long-range missile ahead of the founder's birthday or the upcoming party congress slated for May. (Yonhap)