Controversy is swirling around Donald Trump in his quest for the Republican nomination for president.

At a campaign event Thursday, a supporter told the businessman-turned-politician, "We have a problem in this country - it's called Muslims."

The unnamed man added, "We know our current president is one. You know he's not even an American," CNN reported.

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Trump retorted, "We need this question?" laughing afterward.

Trump came under fire Friday for not correcting the man.

Trump was vocal in asking for President Barack Obama to release his birth certificate. Trump was one of the most prominent of the members of the "birthers," activists who claim that the president is not an American and was born in Kenya, the BBC reported.

The president did release his birth certificate, showing that he was born in Hawaii on Aug. 4, 1961, BBC reported.

Trump responded to the man, not by saying that Obama is a Christian, but rather saying "bad things are happening," adding that he would look into them, the BBC reported.

Democratic presidential front-runner Hillary Clinton went to Twitter to denounce Trump's failure to defend Obama.

Trump's campaign manager told CNN that Trump didn't hear the part of the question accusing Obama of being Muslim.

"All he heard was a question about training camps, which he said we have to look into," Cory Lewandowski said.