Of 16 illegal hacking attacks on Japanese government Web sites that began in January, 12 were carried out through servers in China, according to the Metropolitan Police Department.
The MPD said Friday that one attack occurred through a server in the United States and two via a server managed by the University of Tokyo, adding they could not identify the server in the remaining case.
Several Japanese government and commercial Web sites, including those operated by the Science and Technology Agency, the Management and Coordination Agency and the Mainichi Shimbun newspaper were altered between late January and early February.
Site content was erased and replaced with a message in Chinese protesting a seminar in Osaka in late January that denied the occurrence of the 1937 Nanjing Massacre. The message also criticized the Japanese government for allowing the event to be held in a government building.
The MPD had been investigating the case to determine how the hackers gained access to and erased some data from official Web sites.
They had confirmed earlier that some of the attacks were done through the server at the state-run university and that in the other cases hackers had used servers in the U.S. and China.