RNA - Bernie Sanders and Elizabeth Warren, two Democrat presidential runners, slammed Trump on Twitter, Anadolu Agency reported.
Earlier on Saturday, Trump tweeted a video and retweeted another person's tweet which targeted the Minnesota representative.
"Ilhan Omar is a leader with strength and courage. She won't back down to Trump's racism and hate, and neither will we. The disgusting and dangerous attacks against her must end," Sanders said.
"The President is inciting violence against a sitting Congresswoman—and an entire group of Americans based on their religion. It's disgusting. It's shameful. And any elected leader who refuses to condemn it shares responsibility for it," Warren stressed.
Trump criticized the Muslim lawmaker after comments surfaced of her talking about the Islamophobia Muslims faced in the post-September 11 era.
Omar has been facing attacks for comments she made last week about the September 11, 2001 terrorist attacks.
"Far too long we have lived with the discomfort of being a second-class citizen," Omar said at an event for the Council on American-Islamic Relations (CAIR).
"And frankly, I’m tired of it. And every single Muslim in this country should be tired of it. CAIR was founded after 9/11 because they recognized that some people did something, and that all of us were starting to lose access to our civil liberties," she added.
Twitter users opened several hashtags in support of Omar.