North Korea has fired People's Armed Forces Minister Jang Jong-nam after barely over a year in office, the fourth replacement in the job since leader Kim Jong-un took power in December 2011.
He has been replaced with rising apparatchik Hyon Yong-chol.
Meanwhile Ri Yong-gil, the chief of the Army's General Staff, has not been seen in public for two months, giving rise to rumors that he too has been replaced.
There is speculation that Kim is trying to get the unruly and excessively powerful military under control by way of these frequent replacements.
On Wednesday, North Korean state TV introduced a speaker at a mass rally on the building site of a housing complex for scientists in Pyongyang as "Minister of the People's Armed Forces Comrade Hyon Yong-chol."
Jang was last publicly described as armed forces minister on June 4.
Jang, who is in his 50s, replaced hardliner Kim Kyok-sik in May last year, but has now in turn been replaced by Hyon, a 65-year-old veteran and hardliner.
In July 2012, Hyon replaced Ri Yong-ho as Army chief after Ri, the then military strongman, was purged. But he was demoted to the commander of the Fifth Army Corps in June last year.
Ri Yong-gil has disappeared from view since he accompanied Kim Jong-un on a visit to a long-range artillery unit in April.
"According to North Korean sources, it's highly likely that Ri Yong-gil too has been replaced," said Chung Sung-jang at the Sejong Institute.
Ri, also the fourth Army chief since Kim Jong-un took power, was seen as one of the Young Turks alongside Jang.
Experts speculate that Kim is rapidly oscillating between Old Guards and Young Turks to tighten his grip on the military and leave no one with a sense of security in their position. Another speculation is that Hwang Pyong-so, who rose to military politburo chief replacing Choe Ryong-hae last month, is pulling the strings.
Hwang, who used to work in the Workers Party's Organization and Guidance Department, helped Kim succeed his father. He is also said to have played a leading role in the execution of former eminence grise Jang Song-taek late last year.
"Hwang is taking notes on all instructions given by Kim Jong-un and following him on every visit," a researcher with a government-funded think tank here said. "It's possible that Jang Jong-nam and Ri Yong-gil have been called to account for some problems during Kim's visits to military units."
Park Hyeong-jung of the Korea Institute for National Unification said, "It seems that there's power struggle still underway between the Old Guards, who followed Ri Yong-ho, and the Young Turks who have emerged since Kim Jong-un took power."