WASHINGTON (WASHINGTON POST) - US President Donald Trump on Friday (April 13) tweeted a video attacking Democratic Representative Ilhan Omar for the way she phrased a reference to 9/11, adding fuel to a controversy that has swelled in Republican political circles this week.

By Saturday morning, dozens of lawmakers and public figures had denounced the social media post and the sentiments behind it.

The video showed snippets of comments Omar made last month at a banquet for a Muslim civil rights organisation interspersed with footage of the twin towers burning.

"WE WILL NEVER FORGET!" Trump tweeted, along with the video.

House Speaker Nancy Pelosi denounced the use of the imagery in a statement on Saturday morning from Germany, where she is visiting troops.

"The memory of 9/11 is sacred ground, and any discussion of it must be done with reverence," Pelosi said.

"The President shouldn't use the painful images of 9/11 for a political attack.

"As we visit our troops in Stuttgart to thank them and be briefed by them, we honor our first responsibility as leaders to protect and defend the American people," the statement continued.

"It is wrong for the President, as Commander-in-Chief, to fan the flames to make anyone less safe."

On Thursday, the New York Post had helped set the tone for the president's tweet by publishing a front page that showed her comments over a similar image.

The remarks in question came in March, as Omar, one of the first two Muslim women elected to Congress, spoke about Islamophobia at an event held by the Council on American-Islamic Relations (Cair), a civil liberties group. The white-supremacist shooting that left 50 Muslim worshipers dead at two mosques in New Zealand had occurred the week before.

"For far too long we have lived with the discomfort of being a second-class citizen and, frankly, I'm tired of it, and every single Muslim in this country should be tired of it," she said, in the middle of a roughly 20-minute-long speech.

"CAIR was founded after 9/11 because they recognised that some people did something and that all of us were starting to lose access to our civil liberties. So you can't just say that today someone is looking at me strange and that I am trying to make myself look pleasant. You have to say that this person is looking at me strange, I am not comfortable with it, and I am going to talk to them and ask them why. Because that is the right you have."

The speech had drawn a protest outside at the time and even news coverage from conservative-leaning outlets such as the Washington Times, which noted that she told fellow Muslims to "raise hell", and "make people uncomfortable", as they sought to defend their rights.

But this week conservatives began to fixate on a different portion of the speech, after CAIR posted a video on Tuesday: the four words she used to refer to 9/11, as "some people did something."

The comments were the focus of harsh broadsides from people like Republican Representative Dan Crenshaw, Republican National Committee chairwoman Ronna McDaniel, Donald Trump Jr, and Fox & Friends host Brian Kilmeade, who questioned whether Omar, a Somali refuge, was "an American first."

And after the New York Post put it on such an incendiary cover, some liberals began to speak up against it, saying they felt it was an incitement to violence against Omar, who has been the target of threats and overt Islamophobia.

"Such an ungenerous interpretation of her remarks is only possible if one is inclined to believe that Omar sympathises more with terrorists than her murdered countrymen," Zak Cheney-Rice at New York magazine wrote.

"That she spoke them in the course of decrying Islamophobia makes it especially disconcerting that her political opponents would decontextualise them to fan the flames - she receives regular death threats on the basis of her faith, including from one New York man who threatened recently to 'put a bullet in her... skull'."

Late on Friday night, Beto O'Rourke seemed to respond to the president's tweet with a tweet of his own that prompted criticism for being vague and not directly mentioning Omar: "We are stronger than this president's hatred and Islamophobia. Do not let him drive us apart or make us afraid."

But on Saturday morning, at a townhall in a seafood restaurant near Charleston, South Carolina, O'Rourke described the president's tweet and the video it contained and then denounced it in a monologue that lasted several minutes.

As he spoke, many in the crowd gasped or exclaimed at the description, then applauded O'Rourke's response: that the video is a continuation of rhetoric used by the president and his administration against Mexican immigrants, asylum seekers, Muslims and others.

"There is a cost and there is a consequence to this rhetoric - hate crimes in this country up every single one of the last three years," he said. "This is an incitement to violence against Congresswoman Omar, against our fellow Americans who happen to be Muslim."

At the end of a roundtable with voters in Gary, Indiana, Senator Bernie Sanders hinted at the controversy over Trump's attack on Omar, saying that "the function of a president is bringing our people together," and that the current president was failing at that.

"Even conservative presidents have understood that," Sanders said.

"George W. Bush - I didn't have a lot in common with him. His views were very different than mine," Sanders noted. "But remember what he did after 9/11? He walked into a mosque to say that criminals, terrorists, attacked the United States. Not the Muslim people. That was a conservative Republican. We now have a president who for cheap political gain is trying to divide us up."

The NAACP warned on Twitter that "The President needs to realise that his words have the power to incite hate, violence, and ignorance that is nothing but a detriment to our society."

Numerous House colleagues came to Omar's defence, and her fellow freshmen issued a forceful response to Trump's words. Democratic Representatives Alexandria Ocasio-Cortez, Ayanna Pressley and Rashida Tlaib called for more Democrats to speak out to defend her this week.

"Members of Congress have a duty to respond to the President's explicit attack today," Ocasio-Cortez tweeted. "@IlhanMN's life is in danger."

Several Democratic presidential candidates, including Washington Governor Jay Inslee, former Texas congressman Beto O'Rourke, South Bend, Indiana, Mayor Pete Buttigieg and Julián Castro, a former housing secretary and San Antonio mayor, condemned the president's remarks.

Trump has long wielded 9/11 as a political weapon. In the early part of his presidential campaign, he spread a falsehood that "thousands," of people in New Jersey - where there is a "heavy Arab population," he said - he celebrated as the twin towers came crashing down.

During a primary debate in 2016, he went after rivals like Jeb Bush and Republican Senator Marco Rubio over George W. Bush's failure to prevent 9/11.

"The World Trade Center came down during your brother's reign. Remember that," Trump told Bush.

In 2010, Trump made a highly publicised offer to purchase a contentious site that an Egyptian business planned to build an Islamic community centre on near Ground Zero.