A Chinese court on Monday convicted a man of poisoning dumplings causing around 13 people in Japan and China to fall ill and sentenced him to life in prison, state-run media reported.

Factory worker Lu Yueting was reported to have injected the dumplings with insecticide in 2008 as a protest against his employer over pay.

A court in the northern Chinese city of Shijiazhuang sentenced Lu to life in prison for the crime of "insertion of dangerous substances", China's state broadcaster CCTV said.

Some of the contaminated dumplings were exported to Japan, where nine people fell ill, the official Xinhua news agency previously reported, while four were stricken in China.

The incident ahead of the Beijing Olympics raised tensions between China and its neighbour.

The two countries often have a difficult relationship, mainly over historical issues and territorial disputes.

Japan's Kyodo news agency quoted slightly different figures, stating that the dumplings had made 10 people sick in the country, including a five-year-old girl who became seriously ill.

Japanese consumers avoided Chinese frozen food as a result, and it temporarily disappeared from stores.

Lu was arrested two years after the incident, when Japanese media expressed suspicions about why it had taken Chinese authorities so long to take action.

He confessed to the allegations in a three-hour trial last year, Xinhua reported, adding that he said he felt sorry for the people who became ill.

The agency quoted prosecutors as saying that one person had been made seriously ill while the rest suffered minor sickness, and the incident also resulted in significant financial losses.

He was alleged to have injected insecticide into six to nine boxes of frozen dumplings.

Concerns over Chinese food standards were compounded in late 2008 after six Chinese infants died and almost 300,000 were made ill by milk powder laced with the industrial chemical melamine.