An envelope containing a threatening letter and a razor blade was mailed to Minister of Economy, Trade and Industry Toshihiro Nikai, warning him not to "pander to China," police said Monday.
The letter postmarked May 19 contained typed sentences such as "Do not pander to China," "You have sold assets and riches to China," and "I urge you to commit suicide," according to the police.
It was mailed to a housing complex in Shinjuku Ward, Tokyo, for lawmakers.
Nikai visited Beijing in February to meet with Premier Wen Jiabao in hopes of mending ties soured by Prime Minister Junichiro Koizumi's visits to Yasukuni Shrine.
The letter was signed by a group with a rightwing-sounding name but believed to be fictitious, the police said.
Nikai, a former transport minister, is in his eighth term as a House of Representatives member representing the No. 3 district in Wakayama Prefecture.