US President Donald Trump has attacked Democratic US Representative Ilhan Omar as an "out of control" purveyor of "hate" speech.
He then left for a visit to Minnesota, the state the Muslim-American represents in congress.
Writing on Twitter on Monday, Mr Trump criticised both Ms Omar and House Speaker Nancy Pelosi after he tweeted a video suggesting Ms Omar had been dismissive of the September 11, 2001 attacks.
Ms Omar's and Ms Pelosi's offices had no comment.
The Minnesota congresswoman said she had experienced an increase in death threats, many directly referencing or replying to the president's video.
Ilhan Omar Source: AAP
"Violent rhetoric and all forms of hate speech have no place in our society, much less from our country's Commander in Chief. We are all Americans. This is endangering lives. It has to stop," Omar wrote in a tweeted statement.
The video was no longer a pinned tweet at the top of Mr Trump's Twitter feed, but it had not been deleted.
Marc Lotter, an adviser to Mr Trump's 2020 re-election campaign, denied Trump was inciting violence.
US President Donald Trump has doubled down on his attack on Muslim congresswoman Ilhan Omar. Source: AAP
"I don't think it is the president who's putting her in danger. I think it's her ill-thought-out words that she used to describe the greatest terror attack on the history of United States soil," Lotter told CNN on Monday.
The video tweeted by Mr Trump spliced news footage of 9/11 with a clip from a speech Ms Omar gave last month in which she said "some people did something" in reference to the attacks.
Some Republicans have accused Ms Omar of minimising the September 11 attacks, while critics of the president say he took Omar's words out of context to stoke anti-Muslim sentiment.
The White House said on Sunday that Trump did not wish any harm in his Twitter post about Ms Omar.
The House of Representatives approved a broad resolution condemning bigotry last month after remarks by Ms Omar that some members of both parties viewed as anti-Semitic.
