The recent purge of North Korean leader Kim Jong-Un's once-powerful uncle could herald a period of radical upheaval comparable to China's Cultural Revolution, Japanese defence minister Itsunori Onodera said Thursday.

Pyongyang confirmed Monday that Jang Song-Thaek, once seen as the power behind the throne, had dramatically fallen from grace, with state TV airing humiliating images of him being dragged away by uniformed officers.

"After seeing the footage of Mr Jang Song-Thaek being arrested, it reminded me of scenes one might have seen during the era of China's Cultural Revolution," Onodera said in a speech given at a private think tank in Tokyo.

"North Korea might become a more radical place in the future... that is my concern," he said.

The official news agency KCNA accused Jang, the uncle by marriage and one-time regent for the young Kim, of being a corrupt, drug-taking womaniser bent on building his own faction in the ruling party.

South Korean analysts predicted a sweeping purge would follow, leaving Kim as the undisputed centre of power.

Onodera was speaking about a new national defence policy the government is expected to formally approve next Tuesday.

He pointed to North Korea as a destabilising factor in the region, with its nuclear and ballistic missile programmes adding to the need for Japan to be better able to protect itself.

Like many countries, Japan has an awkward relationship with North Korea, which is complicated by Pyongyang's perceived unwillingness to come clean about the extent to which Japanese nationals were kidnapped in the 1970s and 1980s.

North Korea says all of the people its agents took have either been returned to Japan or have died, but Tokyo disputes this and insists more people are unaccounted for.

The issue is a highly sensitive one for Japan, where vocal and well-supported campaigns ensure it is never far from the top of the diplomatic agenda.