Protesters heckled Donald Trump at a 9,000-person rally in Michigan on Monday, interrupting his speech more than 10 times with shouts before security guards ejected them from the event.

Trump, the front-runner for the Republican presidential nomination, alternated between criticizing the hecklers and asking the guards leading more than a dozen people out of the room to "be gentle."

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The interruptions sapped some of the energy Trump often builds during his speeches, but did not dampen the enthusiasm of his supporters.

The crowd cheered Trump's pledge to build a border wall, his searing criticism of political opponents and repetition of his campaign slogan "make America great again."

At rallies this month in South Carolina and Nevada and a luncheon in New York, protesters have interrupted the candidate, attacking his controversial proposal to ban all Muslims from entering the United States and other statements of his they say are racist or discriminatory.

"I said Trump you don't represent us, as in black people, and also I'm a Muslim," said Mai Eltahir, 19, a student at the University of Michigan in Flint who traveled to Grand Rapids.

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At one point, after halting remarks on trade to wait for hecklers to be ejected, Trump suggested the protesters might be "drugged out."

He chided another group for being "so weak" they would not resist security guards' directions to leave. Trump also said he wondered why the protesters would bother standing up and drawing attention to themselves "in a group of 9,000 maniacs that want to kill them," referring to the crowd.

One audience member punched a protester, a young man alone near an exit, before a guard came to lead him away.