Donald Trump's homeland security secretary, Kirstjen Nielsen, dramatically quit her post on Sunday night, becoming the latest in a series of high-profile figures to leave his administration.

Ms Nielsen's departure was confirmed by the President on Twitter and came after she met Mr Trump at the White House.

It is understood Mr Trump was unhappy with her performance at Homeland Security as he moved towards taking a tougher line on immigration.

Only last week, speaking in Las Vegas, the US president declared that "our country is full" as he placed immigration firmly on the agenda of his re-election campaign.

According to reports in Washington, the final straw came when Ms Nielsen was blindsided by the White House decision to rescind the nomination of Ronald Vitello as head of Immigration and Customs, one of the most senior officials in her department.