The US agency responsible for maintaining and designing the nation’s cache of nuclear weapons was among those breached by a hack of Microsoft Corp.’s SharePoint document management software, according to a person with knowledge of the matter.

The tech giants have evidence that Chinese hackers are exploiting the new bug, but warned "multiple actors" are also hacking into affected SharePoint systems.

US tech giant Microsoft has pointed the finger at China amid a wave of cyberattacks on firms and government agencies worldwide, announcing on Tuesday that it has identified three Chinese hacker groups responsible for the damage so far.