Japanese police are investigating a Chinese diplomat who is suspected of spying and engaging in unlawful commercial activities during his recently-ended stay in Tokyo, investigative sources said Tuesday. In mid-May, the police made a request to the Chinese Embassy in Tokyo through Japan\'s Foreign Ministry that the diplomat turn himself in for questioning over the commercial activities, which are apparently in violation of the Vienna Convention on Diplomatic Relations, the sources said, according to Japan\'s News Agency (Kyodo). But the embassy turned down the request and the 45-year-old first secretary, who was from an intelligence unit of the Chinese army, returned to China, according to the sources.