Leading Republicans in the US have called for an investigation into leaks that led to the resignation of National Security Adviser Michael Flynn. The Heads of the House Oversight and Judiciary Committees are concerned potentially classified information was released. <br/><br/>Mr Flynn is alleged to have discussed US sanctions with Russia's Ambassador in calls before his own appointment. It is illegal for private citizens to conduct US diplomacy. President Donald Trump, who is also facing questions over his ties with Russia, accused US intelligence agencies of leaking information about Mr Flynn's phone calls.