US National Security Adviser Michael Flynn has resigned.

Michael Flynn US National security adviser has resigned over accusations he discussed with US sanctions with Russia before Donald Trump took in the office

Flynn is said to have misled officials about his call with Russia's ambassador before his own appointment. It is illegal for private citizens to conduct US diplomacy.

US reports earlier said the White House had been warned about the contacts last month and was told Mr Flynn may be vulnerable to Russian blackmail.

The national security adviser is appointed by the president to serve as his or her chief adviser on international affairs and defense.