Donald Trump claims the US presidential election is being “rigged” by a “dishonest media” and at “many polling places”.
It follows the start of early voting and voting by mail in many states.
His accusations appear to contradict his running mate Mike Pence who had earlier said Republicans would accept the outcome of the November 8 poll.
Meanwhile Trump has blamed supporters of his Democratic rival, Hillary Clinton for the firebombing of a Republican campaign office in North Carolina. Someone also spray-painted graffiti including a swastika on a wall.
Using social media Trump called those responsible “animals representing Clinton”.
While Clinton, also using social media condemned the attack describing it as horrific and unacceptable.
While Trump is busy questioning the legitimacy of the US election process, new opinion polls have Hillary Clinton leading the race for the White House albeit by either 4 and 11 points.
This week’s focal point is the third and final debate between the two contenders which is on Wednesday in Las Vegas.