WASHINGTON - US President Donald Trump has ordered the firing of the US Secret Service director, CNN reported on Monday, one day after the resignation of another top national security official, Homeland Security Secretary Kirstjen Nielsen.

Trump instructed his acting chief of staff Mick Mulvaney to fire Secret Service Director Randolph Alles, CNN reported, citing multiple administration officials. One official described the firings as "a near-systematic purge" at the Department of Homeland Security.

The White House did not immediately respond to a request for comment.