Classified Japanese diplomatic information was leaked following Chinese cyberattacks on the Foreign Ministry in 2020, a government source said Monday, exposing the nation's digital vulnerability.

Japan detected the large-scale attack and release of diplomatic telegrams during a period of government under then-Prime Minister Shinzo Abe, the source said, but the nature of the leaked information is still publicly unknown.

Tokyo and Washington discussed countermeasures in the wake of the leak of the diplomatic telegrams, which are highly confidential documents exchanged daily between the ministry and diplomatic missions abroad, the source said.