​Russia's social media blitz to influence the 2016 US election was part of a global "phenomenon" in which a broad spectrum of governments and political parties used internet platforms to spread junk news and disinformation in at least 48 countries last year, an Oxford University study has found.

Including US government programmes aimed at countering extremists such as Islamic fundamentalists, about $500 million (734 million NZ) has been spent worldwide on research, development or implementation of social media "psychological operations" since 2010, the authors estimated.