Nuclear-armed North Korea has ridiculed US President Barack Obama’s visit to Hiroshima as the "childish" diplomatic ploy of a "nuclear war fanatic."

Nuclear-armed North Korea has ridiculed US President Barack Obama's visit to Hiroshima as the "childish" diplomatic ploy of a "nuclear war fanatic."

In a commentary released late Thursday, the North's official KCNA news agency said Obama's decision to become the first sitting US president to visit the site of the 1945 atomic bomb strike was an act of stunning hypocrisy.

"It is a childish political calculation," the agency said.

"Even if Obama visits the damaged city, he cannot hide his identity as a nuclear war fanatic and nuclear weapons proliferator," it added.

Heavily sanctioned for its four nuclear tests, Pyongyang insists its entire weapons program is an unavoidable response to decades of US nuclear hostility.

Obama was due to lay a wreath in Hiroshima later Friday at a memorial to the bombing which ultimately claimed the lives of around 140,000 people.

The KCNA commentary also questioned Tokyo's motives in organizing Obama's visit, saying it was playing up the notion of Japan as a victim of war, and shifting the focus away from the pain its colonial ambitions and wartime aggression inflicted on others.

"Japan seeks to put under the carpet its true colors as a provocateur of the war and aggressor ... despite its past crimes," the agency said.

The Korean peninsula suffered more than three decades of harsh Japanese colonial rule which only ended with Japan's surrender following the Hiroshima and Nagasaki bombings.