“He has given aid and comfort to white supremacists,” Ms Warren said, while campaigning in Iowa on Wednesday evening.
“He’s done the wink and a nod. He has talked about white supremacists as fine people.
“He’s done everything he can to stir up racial conflict and hatred in this country,” she said, according to The New York Times.
Asked if she believed the president himself was a white supremacist, the Massachusetts senator said: “Yes.”
Mr Trump has been criticised for his racism in the wake of the El Paso massacre.
The shooting was allegedly carried out by a gunman who first posted a document filled with anti-immigrant rhetoric online.
He then opened fire in an El Paso Walmart, killing 22 and wounding more than two dozen more.
Beto O’Rourke, a former congressman who once represented El Paso, also criticised Mr Trump on Wednesday.
“He is. He has made that very clear,” he said, when asked if he believed the president was a white supremacist.
“He dehumanised those who do not look and pray like the majority of people here.
“He said I wish we had more immigrants from Nordic countries because those from Haiti bring AIDS, those from Africa are s****** nations.”
The president defended himself on Twitter after being repeatedly criticised over his rhetoric.
“The Dems new weapon is actually their old weapon, one which they never cease to use when they are down, or run out of facts, RACISM!” Mr Trump said.
“They are truly disgusting!
“I will be putting out a list of all people who have been so (ridiculously) accused!”
The 73-year-old visited shooting survivors in El Paso on Wednesday.
Protesters booed the president while he was driven to a hospital in the city.
Mr Trump also visited Dayton, Ohio where a gunman killed nine people in a mass shooting which occurred shortly after the El Paso massacre.
When his motorcade made its way to the Miami Valley Hospital in Dayton, to meet survivors, around 100 people were gathered blocks away in a grassy field where they held signs reading “Dump Trump” and “Do Something!”.
Pro-Trump flags were also seen in the city.