A television station in northeast China's Harbin is working on a 30-episode serial documentary about the "Oriental Machino," a string of fortresses built in China by the Japanese during World War II.

Production of the documentary should be complete by August 15, marking the 60th anniversary of the World Anti-Fascism War and China's Anti-Japanese War, said Xian Mingzhe, the director.

While occupying northeast China in the early 1930s, the Japanese troops built the "Oriental Machino," 14 clusters of fortresses along China's border with Russia and Mongolia.

The Dongning Fortress, one of the 14, is where Soviet and Japanese troops fought the last battles of World War II.

According to some Chinese historians, several million laborer and POWs from China, Korea and the Soviet Union were slaughtered after they were forced to construct the fortresses.

The "Oriental Machino" has been one of the major mysteries of World War II, because the Japanese government would not comment on it. The serial is aimed at unveiling the truth, said Xian.