An unexploded bomb in a school's memorial center is attracting hundreds of visitors every day ahead of the 70th anniversary of World War II, as it was used as a school bell from the early 1950s to the late 1990s for a reminder of the national humiliation.

An unexploded bomb in a school's memorial center is attracting hundreds of visitors every day ahead of the 70th anniversary of World War II, as it was used as a school bell from the early 1950s to the late 1990s for a reminder of the national humiliation.

Langzhong Middle School, located in China's southwest province of Sichuan, was among the targets of Japanese air strikes in 1941, during China's War of Resistance against Japanese Aggression. A school teacher later found this unexploded bomb in the early 1950s from the debris and suggested it could be turned into a school bell after being safely dismantled.

"This is hard evidence of Japanese's military aggression against China," said Yan Xiaoyong, a teacher in the school told Chinanews.com. "We now use an electric bell to signal every class, but this bomb-turned bell is used on Sept. 18 every year to commemorate the Mukden Incident, which was the beginning of Japan's invasion of northeast China in 1931."

The Japanese army launched four major air strikes in Langzhong, a city of strategic importance in northern Sichuan, which served as a transit station for goods supply from the Allied powers.

The serial attack caused over 200 deaths and left over 500 wounded.