United States President Donald Trump has attacked a group of Democratic congresswomen, telling them to go back to the "broken and crime infested places from which they came," ignoring the fact the women are American citizens and all but one was born in the US.

Key points: Mr Trump alleged that some congresswomen came from "crime-infested" countries

Mr Trump alleged that some congresswomen came from "crime-infested" countries A majority of the women he alluded to are US-born from non-white backgrounds

A majority of the women he alluded to are US-born from non-white backgrounds This drew a fierce reaction from representatives across the US political divide

Over three tweets posted on Sunday (local time), Mr Trump said a number of the Democratic Party's progressive congresswomen "originally came from countries whose governments are a complete and total catastrophe, the worst, most corrupt and inept anywhere in the world".

He did not identify the "progressive congresswomen" in his tweet.

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It's assumed Trump is talking about 'the squad'

They are:

New York congresswoman Alexandria Ocasio-Cortez

New York congresswoman Alexandria Ocasio-Cortez Minnesota congresswoman Ilhan Omar

Minnesota congresswoman Ilhan Omar Massachusetts congresswoman Ayanna Pressley

Massachusetts congresswoman Ayanna Pressley Michigan congresswoman Rashida Tlaib

All four were part of the record number of women and minorities that were elected to the US House of Representatives in the 2018 midterm elections.

The group picked up the nickname for their shared progressive politics, and their willingness to publicly call out not only Mr Trump and Republicans, but their own party as well.

Only Ms Omar was foreign-born, but she emigrated to the US at age 12 after spending much of her childhood in a Kenyan refugee camp.

Ms Ocasio-Cortez, who is of Puerto Rican descent, was born in the Bronx, New York, and raised in suburban Westchester County.

Ms Pressley, the first black woman elected to the House from Massachusetts, was born in Cincinnati.

Ms Tlaib was born to Palestinian parents in Detroit.

Democrats swiftly labelled the tweets 'white nationalism'

Mr Trump has come under fire for alleged support for white nationalists during his first term. ( AP: Eric Gay )

Democratic House Speaker Nancy Pelosi said the President wanted to "make America white again".

"I reject @realDonaldTrump's xenophobic comments meant to divide out nation," Ms Pelosi tweeted.

The four congresswomen who make up "the squad" were quick to do the same.

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Ms Tlaib said Mr Trump's "dangerous ideology is the crisis", Ms Ocasio-Cortez said that Mr Trump was "angry" because he could not "conceive an America that includes us", Ms Pressley said that Mr Trump's tweets are what "racism looks like" while Ms Omar said the President was "stoking white nationalism".

According to the Washington Post, at least 27 congressional Democrats had used the word "racist" or "racism" to describe Mr Trump's tweets.

Addressing the criticism, Mr Trump did not back down from his original comments.

"So sad to see the Democrats sticking up for people who speak so badly of our country and who, in addition, hate Israel with a true and unbridled passion. Whenever confronted, they call their adversaries, including Nancy Pelosi, 'RACIST'," he tweeted.

Republicans haven't weighed in

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Republican congressional leaders, including Senate Majority Leader Mitch McConnell, did not respond to requests for comment, nor did Senator Tim Scott of South Carolina, the only Republican black senator.

Mark Morgan, the acting commissioner of US Customs and Border Protection, said this in a previously scheduled appearance on "Face the Nation" on CBS:

"You're going to have to ask the President what he means by those specific tweets," he said.

So far, only former Republican representative Justin Amash of Michigan, a Trump critic who left the party just over a week ago to become an independent, called the remarks "racist and disgusting".

It's not the first time Mr Trump has been embroiled in a racism controversy.

In 2017, following violence between white nationalists and anti-racism campaigners, Mr Trump said there was "fault on both sides" for the violence that erupted in Charlottesville, Virginia.

A day later he explicitly condemned right-wing racism, but he reiterated that his initial comments made up a "fine statement".

From 2011 until late into his presidential campaign in 2016, Mr Trump repeatedly fuelled conspiracy theories that former president Barack Obama was not an American citizen.

Trump and congresswomen have history

Sorry, this video has expired Can US President Donald Trump be impeached?

Ms Tlaib made waves just hours after she was sworn in, when she told a crowd of supporters what she intended to do in Washington:

"We're going to go in there and we're going to impeach the motherf***er."

Ms Omar said she has received death threats after Mr Trump tweeted out a video of the congresswoman talking about the September 11, 2001 terrorist attacks.

Mr Trump also called for Ms Omar to resign from Congress after she apologised for suggesting other politicians support Israel because they are paid to do so.

And Ms Ocasio-Cortez, the Democrats' own social media star, has frequently targeted the President on his medium of choice:

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ABC/AP