Around 1,000 Chinese workers went on strike after their Japanese boss denied Tokyo had invaded China and said its 1930s actions were to "help" the country escape colonial rule, state-run media reported Wednesday.

The walkout took place on Tuesday, the same day that Japan loosened the bonds on its powerful military, proclaiming the right to go into battle in defence of allies, in a highly controversial shift in the nation's post-World War II pacifist stance.

It came amid tensions between the two nations over wartime history and a territorial dispute in the East China Sea.

Masataka Kataoka, the head of Alps Electric, a Japanese investor in joint venture Chang'an Rihua Electronic Plant, said at a managerial meeting that Japan did not invade China, the Global Times reported.

Tokyo had moved to "help lift China out of colonial rule from countries like the US", he said, according to the paper, which often takes a nationalist tone and is close to China's ruling Communist Party.

Workers gathered in protest for at least three hours, it said, until Kataoka apologised at the plant in Dongguan, in the southern province of Guangdong.

The China Daily carried a picture of Kataoka doing so, using a megaphone.

The apology lasted six minutes, the Southern Metropolis Daily reported, and ended with a "slight bow" to the workers.

The factory makes electronic products and parts for international brands including Japan's Hitachi, Panasonic, Sony and Pioneer, the China Daily said.

Japan invaded China in the 1930s and the two countries fought a full-scale war from 1937 until Tokyo's defeat in World War II in 1945.

Relations between the Asian giants soured in 2012 when Tokyo nationalised some of the disputed islands known as Diaoyu in China and Senkaku in Japan.

Chinese protesters took to the streets in major cities at that time, attacking Japanese diplomatic facilities and businesses, harassing individual Japanese and turning over vehicles made by the country's manufacturers in demonstrations initially condoned by authorities, who eventually restricted them.

Tensions escalated again late last year when Abe visited the controversial Yasukuni shrine in Tokyo that honours Japan's war dead, including convicted war criminals.

Japan's Jiji Press cited an Alps Electric official as saying Kataoka made the remarks because he wanted to express his strong hope for efforts by Chinese firms.