Latest: Trump says investigation will clear him of collusion accusations

Latest: Donald Trump has said a thorough investigation will confirm there was "no collusion" between his presidential election campaign and any foreign entity.

Update 00:42am: Donald Trump has said a thorough investigation will confirm there was "no collusion" between his presidential election campaign and any foreign entity.

Earlier: The US Justice Department on has appointed former FBI director Robert Mueller as a special counsel to oversee a federal investigation into potential coordination between Russia and the Trump campaign during the 2016 presidential election.