A team of Chinese and Japanese experts have found a cache of some 500 bombs from World War II buried in north-eastern China.
Wartime Japan had expansionist ambitions in China
The bombs were first discovered last month by a farmer in a yard used during the war as an airstrip, said China's Xinhua news agency.
Many are said to contain potentially fatal doses of toxic gases.
Experts say the bombs were left by the retreating Japanese army as its puppet-state of Manchukuo collapsed.
Japan has committed millions of dollars to clean up thousands of chemical weapons left behind by its troops at the end of the war.
The bombs were found in a 4-sq-m (43-sq-ft) site in Touzhan village, near Qiqihar city in the province of Heilongjiang, an official told Xinhua.
A local farmer, Dong Liyan, came across the weapons on his land.
According to the agency, a Japanese regiment used to be deployed on the site, which was used by the Japanese as an airport during WWII.
In the 1930s, the Japanese army occupied Manchuria - renaming it Manchukuo - and then tried to extend its control along the length of China's coast until its defeat by Allied forces and surrender in 1945.
A team of Chinese and Japanese experts arrived in Qiqihar on Wednesday to begin preparations to dispose of the weapons, in a process expected to take about 10 days.
Japan estimates that more than 700,000 chemical weapons were abandoned by its armies in China, though some Chinese experts say two million may remain to be discovered across the country.
About 2,000 Chinese people have been involved in accidents involving the discarded weapons since the end of the war, Xinhua said, but it did not specify the severity of the injuries incurred.
Japan has until 2007 to find and destroy the weapons under the UN Chemical Weapons Convention, but there are doubts it can achieve the task in time.
It has budgeted some 60 billion yen ($547m) for the work over the last five years, AFP news agency reported.