Hackers sponsored by the Chinese state have breached a number of U.S. government institutions, including the agency responsible for overseeing the security of America’s nuclear arsenal, Microsoft warned.

Researchers say Chinese actors, along with other criminal hackers, exploited a security flaw in SharePoint software widely used by governments and businesses.

Chinese "threat actors" have hacked Microsoft's SharePoint document software servers and targeted the data of the businesses using it, the firm has said.