Filming of a documentary about the atrocities of Japan's notorious Unit 731 during World War II (WWII) began in the northeastern Chinese city of Harbin on Wednesday.

The documentary entitled "731" will interview witnesses and scholars and disclose historical archives.

The documentary, consisting of five 60-minute episodes, will be jointly shot by the Harbin municipal government and China Central Television. It is expected to be broadcast by the end of the year.

It will be shot in China, the United States, Russia and Japan.

"The harm the invading Japanese army did to the Chinese people could never be compensated," said Li Fengqin, 73, whose father was killed in 1941 by Unit 731 troops.

"We should keep in mind the history and never forget the disaster," she said.

Unit 731 was a top-secret biological and chemical warfare research base established in Harbin in 1935, serving as the nerve center of Japan's biological warfare in China and Southeast Asia during WWII.

At least 3,000 people were killed in experiments on humans at Unit 731. Civilians and prisoners of war from China, the former Soviet Union, the Korean Peninsula and Mongolia all perished at the hands of the Japanese.

The retreating Japanese invaders blew up the base when the Soviet Union army took Harbin in 1945.