WASHINGTON (AFP) - US President Donald Trump on Friday (July 19) slammed what he called "crazed" media coverage of taunts targeting a Somali-born Democratic lawmaker during one of his rallies, alleging political bias against him.

Facing a mounting backlash over the cries of "Send her back" aimed at congresswoman Ilhan Omar, Mr Trump accused the media of a "sick partnership" with his Democratic opponents.

"It is amazing how the Fake News Media became 'crazed' over the chant 'send her back' by a packed Arena.... but is totally calm & accepting of the most vile and disgusting statements made by the three Radical Left Congresswomen," Mr Trump tweeted.

"Mainstream Media, which has lost all credibility, has either officially or unofficially become a part of the Radical Left Democrat Party," he continued.

"It is a sick partnership, so pathetic to watch!" Mr Trump ignited a firestorm at the weekend when he urged Ms Omar and three other progressive Democratic congresswomen of colour - all American citizens and three of them US-born - to "go back" to their countries of origin.

Despite the uproar over his comments, condemned as "racist" by the Democratic-controlled US House of Representatives, Mr Trump stepped up his attacks at a rally in North Carolina on Wednesday (July 17), where the incendiary chants broke out.

Mr Trump later sought to disavow the chants, but television footage showed he let them continue for more than 10 seconds before he resumed speaking.

Ms Omar has branded Mr Trump a "fascist" in response.