The African group of ambassadors to the United Nations has demanded an apology from Donald Trump, after the US president reportedly aimed a racist remark at some Caribbean nations and Africa.

Trump criticised immigration to his country from El Salvador, Haiti and the African continent, by calling the group "shithole countries" at a meeting with Congress members at the White House on Thursday, according to US media.

"The African Union mission to the UN is extremely appalled at, and strongly condemns the outrageous, racist and xenophobic remarks attributed to the US president as widely reported by the media," Martha Ama Akyaa Pobee, Ghana's ambassador to the UN, said on Friday.

The group has demanded a retraction and apology from Trump.

According to US media reports, citing people with knowledge of the conversation, Trump asked during a conversation about immigration: "Why are we having all these people from shithole countries come here?"

Trump suggested the US should instead focus its immigrant entry policy on countries such as Norway.

Following an emergency session of the African diplomats, Pobee added that the group "is concerned at the continuing and growing trend from the US administration towards Africa and people of African descent to denigrate the continent and people of colour".

The ambassadors' reaction comes after the 55-nation African Union said it was "frankly alarmed".

"Given the historical reality of how many Africans arrived in the United States as slaves, this statement flies in the face of all accepted behaviour and practice," AU spokeswoman Ebba Kalondo said on Friday.

Global outrage

Trump's latest comments have sparked global outrage and have been widely condemned as racist and extremely offensive.

Al Jazeera's Kimberly Halkett, reporting from Washington, DC, said: "The calls for the president to apologise for his remarks are intensifying inside and outside the US, but for now, that apology does not appear likely."

Rupert Colville, a spokesman with the UN human rights office, earlier slammed Trump's "vulgar language".

"You cannot dismiss entire countries and continents as shitholes ... I'm sorry, but there's no other word one can use but racist," Colville said.

Trump denied the racist remarks, tweeting on Friday that the language he used "was tough, but this was not the language used", as he called for a "merit-based system of immigration and people who take our country to the next level".

Never said anything derogatory about Haitians other than Haiti is, obviously, a very poor and troubled country. Never said “take them out.” Made up by Dems. I have a wonderful relationship with Haitians. Probably should record future meetings - unfortunately, no trust! — Donald J. Trump (@realDonaldTrump) January 12, 2018

He later tweeted that he has "never said anything derogatory about Haitians other than Haiti is, obviously a very poor and troubled country".

The Republican president has also privately defended his remarks, saying he was only expressing what many people think but will not say about immigrants from economically depressed countries, the Associated Press reported.

Democrats have dismissed Trump's denial of the offensive comments, with Senator Dick Durbin, who attended the meeting, disputing Trump's account.

"He said these hate-filled things and he said them repeatedly," Durbin told reporters on Friday.

Members of his own Republican party have also distanced themselves from Trump's comments.

"It is incomprehensible that these words came out of the mouth of the president of the United States of America, a country that was founded on being free from discrimination," said Ileana Ros-Lehtinen, a Republican congresswoman.