Several House of Councilors members have received emails carrying Trojan horse programs designed to breach the security of computer systems, Deputy Chief Cabinet Secretary Tsuyoshi Saito said Wednesday, revealing the cyber-attacks.

Previously, members of the House of Representatives, various ministries, including the Foreign Ministry and its overseas diplomatic missions, as well as major defense contractors, have come under similar attack.

According to Saito, seven Upper House lawmakers received emails with attachments similar to ones sent to three Lower House members in July that installed programs on the Lower House server and the computers of the three lawmakers. However, Saito said Wednesday that the Upper House server was unaffected and the lawmakers' PCs were currently being checked. Saito added the National Information Security Center has been instructed to provide information and advice to the Upper House secretariat.

Later in the day, Prime Minister Yoshihiko Noda stressed that the government would devote itself to strengthening measures against cyber-attacks.

"The government views that taking measures against cyber-attacks is an important task for national security and crisis management in the modern IT society," Noda said during an Upper House plenary session. "While cooperating with other related countries beginning with the U.S., the government will strive as one to take measures against cyber-attacks."

The prime minister added that police were investigating.

"The police have been diligently investigating and collecting information on these cases and if violations of the law are found, I am aware that the police will take strict action," Noda said.