US congresswoman Ilhan Omar has blamed Donald Trump for a spike in death threats against her after the president tweeted a video suggesting she was dismissive of the 9/11 terrorist attacks.

"This is endangering lives," she said, accusing Mr Trump of fomenting right-wing extremism. "It has to stop."

Mr Trump has been heavily criticised for the tweet and accused by some of inciting violence against Ms Omar, who became one of the first Muslim women to sit in Congress in January.

The video included a snippet from a recent speech Ms Omar gave to the Council on American-Islamic Relations, in which she described the September 11, 2001, terrorist attack on the World Trade Center as "some people did something," along with news footage of the hijacked airplanes hitting the Twin Towers. Mr Trump shared the video along with the caption: "we will never forget!"

Ms Omar was accused of being flippant in describing the perpetrators of the attacks that killed nearly 3,000 people. She later sought to defend herself by tweeting a quote from President George W Bush, in which the Republican president referred to the attackers as "people" just days after the tragedy.