The 2004 suicide of a staff member at the Japanese Consulate General in Shanghai came after the Chinese forced him to hand over information to break government codes by exploiting an illicit relationship he was allegedly having with a woman, Foreign Minister Taro Aso suggested Saturday.

"He killed himself as he could not sell out his country. It is clear as he left a suicide note," Aso told a public meeting in Tokyo. "It is natural (for Japan) to deal with the issue in a determined manner."

The government has so far refrained from releasing details of the suicide, citing privacy and the wishes of the man's family. It has only said there were "regrettable acts" on the part of Chinese security agents.

Aso also said diplomatic staff are at risk of exploitation through sex, and the Foreign Ministry needs to keep this in mind.

"As a diplomat's face is (usually) not attractive, so he or she should be trained to be cautious when approached (by a person of the opposite sex), and we often hear about such cases as this in (diplomatic) society," Aso said.

"Training, education and discipline are extremely important," he went on to say. "The Foreign Ministry needs to do some serious soul-searching."

The suicide, which was made public last month, has further strained ties between Japan and China.