Children visit the 9.18 History Museum in Shenyang, capital of northeast China's Liaoning Province, on Friday, September 18, 2009, the 78th anniversary of the September 18 Incident, which marked the beginning of the Japanese invasion of China. [Photo: CFP]

Sirens wailed in a number of Chinese cities Friday to remind people of the Sept. 18 invasion and occupation by Japanese troops in 1931.

"We should not forget the past. The history tells us that we will be beaten if we are weak," said Yang Jianhua, a 56-year-old worker who beat the bell at the 9.18 History Museum.

Dozens of cities across China including Harbin, Changchun and Xi'an also sounded the alarms at 9:18 a.m. to remind the people of the humiliating history.

On Sept. 18 in 1931, Shenyang resounded with the noise of cannons and explosions when Japanese forces attacked the barracks of Chinese troops. The move marked the beginning of a Japanese occupation that lasted 14 years.

A history museum in Changchun, capital of northeast China's Jilin Province, opened to the public for free as from Sept. 18. The Museum covers 10,600 square meters with more than 3,000 historical documents and materials.

An exhibition in Beijing displayed 220 photos and 260 items of historical relics on ordinary people's fighting against Japanese troops. The exhibition will run until April 30 in 2010.