US President Donald Trump took aim at progressive Democratic congresswomen Sunday, telling them to "go back" where they came from in remarks that sparked yet another firestorm over his views on race and immigration. Trump -- whose comments were branded "racist" and "xenophobic" by Democratic presidential candidates and senior legislators -- last year reportedly referred to countries in Africa as "shithole" nations, and has spoken of an "invasion" of migrants. He was also a leading proponent of the "birther" conspiracy theory that Barack Obama was not born on US soil and therefore could not legally be president. On Sunday, Trump referred on Twitter to "'Progressive' Democrat Congresswomen" in remarks that appeared to be aimed at a group of outspoken relatively young, liberal women of color, all first-time members of the House of Representatives. These include Alexandria Ocasio-Cortez of New York, Ilhan Omar of Minnesota, Rashida Tlaib of Michigan and Ayanna Pressley of Massachusetts. They "originally came from countries whose governments are a complete and total catastrophe, the worst, most corrupt and inept anywhere in the world," Trump tweeted. He accused the women of "viciously telling the people of the United States, the greatest and most powerful Nation on earth, how our government is to be run." "Why don't they go back and help fix the totally broken and crime infested places from which they came. Then come back and show us how it is done," Trump wrote. - 'What racism looks like' - Trump did not identify the targets of his comments by name. But in a tweet later in the day, he said they "hate Israel with a true and unbridled passion," indicating he may have been referring to Omar and Tlaib, who have recently been embroiled in controversies related to the Jewish state. Tlaib, who was born in Detroit, is the first American of Palestinian descent elected to Congress, while Omar, who fled war-torn Somalia as a child and came to the United States as a refugee, is the first black Muslim woman in Congress. Ocasio-Cortez, who was born in New York, is of Puerto Rican ancestry, and Pressley, who was born in Cincinnati, is the first African American elected to Congress from Massachusetts. The four hit back at Trump on his favored social media site. "I am fighting corruption in OUR country. I do it every day when I hold your admin accountable as a U.S. Congresswoman," Tlaib tweeted. "You are stoking white nationalism bc you are angry that people like us are serving in Congress and fighting against your hate-filled agenda," Omar wrote on Twitter. "THIS is what racism looks like. WE are what democracy looks like," Pressley wrote over a screenshot of Trump's tweets, while Ocasio-Cortez tweeted that Trump is "angry because you can't conceive of an America that includes us." - 'Making America white again' - They were joined in their criticism of Trump by Democratic presidential candidates as well as leaders from the party, which holds the majority in the House of Representatives. "Racism and xenophobia have no place in America," tweeted former vice president Joe Biden, the frontrunner for the 2020 Democratic nomination. Senator Elizabeth Warren termed Trump's comments "a racist and xenophobic attack on Democratic congresswomen," while Senator Kamala Harris tweeted: "Let's call the president's racist attack exactly what it is: un-American." "That's a racist tweet," Assistant House Speaker Ben Ray Lujan, the highest-ranking Latino member of Congress, said on "Fox News Sunday." House Speaker Nancy Pelosi has warned her party to avoid the "menace" of liberal policies pushed by Ocasio-Cortez and other progressives, if Democrats hope to beat Trump in the 2020 election. But on Sunday, she criticized Trump's "attack." "I reject @realDonaldTrump's xenophobic comments meant to divide our nation," she tweeted. Trump's remarks, she said, reaffirmed "his plan to 'Make America Great Again' has always been about making America white again." Senior Republican lawmakers were notably silent on Trump's comments, while the president later doubled down on his remarks, attacking Democrats for coming to the lawmakers' defense. "So sad to see the Democrats sticking up for people who speak so badly of our Country," Trump tweeted.