North Korea's military chief, a close ally of the country’s new leader Kim Jong Un, has been relieved of all his posts because of illness, North Korea’s official KCNA news agency said on Monday.

The political bureau of the ruling Workers' Party decided to relieve Ri Yong Ho, 70, of all his duties during a meeting on Sunday, the report said.

Besides heading North Korea’s one-million strong military since 2009, Ri was also a top figure in the Workers' Party. He often appeared at state occasions beside Kim Jong-il, the late father of the current North Korean leader, and has been seen accompanying Kim Jong Un on visits to military bases in recent months.

It was not immediately clear who would replace Ri. State media reports have not elaborated on his health condition.

Some observers have expressed skepticism over the announced reason for Ri’s retirement.

"We cannot rule out the possibility that the army chief of the General Staff Ri Yong Ho was dismissed on account of Kim Jong Un's unsatisfactory military grip or as a result of a power struggle in North Korea,” South Korea’s Yonhap news agency quoted Chang Yong-suk from the Institute for Peace and Unification Studies at Seoul National University, as saying.