A man mourns the victims of the 1945 Bombing of Tokyo at an altar set up inside a shrine in Tokyo, March 12, 2016. Yonhap

North Korea on Monday urged Japan to investigate and apologize to Korean victims killed in the U.S. firebombing of Tokyo in 1945, near the end of World War II, a day before Japan is set to mourn the victims of the devastating air raid.

The demand was issued by a North Korean association of those mobilized for forced labor by Japan during the country's 1910-45 colonial rule over Korea and their bereaved families, in a statement published by the Korean Central News Agency (KCNA).

On the night of March 9-10, 1945, the U.S. Air Force conducted a devastating firebombing raid on the Japanese capital, dropping bombs from hundreds of heavy bombers and burning most of eastern Tokyo in an effort to force a surrender, in an event known as the Bombing of Tokyo.

About 100,000 people were estimated to have been killed in this single-day air attack, with about 10 percent believed to be Koreans. Every year on March 10, Japan mourns the victims of the air raid, although its Korean victims reportedly remain uncompensated.

"At that time the Japanese imperialists kept Koreans in custody in groups, claiming that Koreans who had been subjected to subhuman maltreatment and humiliation, dangerous and toilsome labor could escape in the confusion of air raids," the association said. "As a result, many Koreans died an accidental death."

North Korea accused Japan of "burying the Korean dead in 67 places of parks, temples and campuses," without investigating their identities, under the pretext of the emperor's "junket" to the area.

"Later, they committed such hideous unethical crimes as digging out the dead and dealing with the remains of Koreans at will," the association noted.

It urged Japan to make a thorough apology and provide reparations for the victims and their bereaved families "for the thrice-cursed crimes of pushing innocent people into death."

The group also called for "a full investigation" into the remains of Korean victims that have been left unattended for 80 years and for the public disclosure of the investigation.

"It is the unshakable will of all the Korean people to certainly give vent to the deep-rooted grudge of the victims who lost their flowery youth and precious lives due to the forcible drafting by the Japanese imperialists and of their bereaved families," the statement said. (Yonhap)