Washington - Republican front-runner Donald Trump tumbled into fresh controversy Friday after declining to challenge a questioner at a campaign event who asked when the United States can "get rid of" Muslims.
"We have a problem in this country, it's called Muslims. We know our current president is one, you know he's not even an American," an unidentified man began a question to Trump at the billionaire real estate magnate's campaign stop late Thursday in Rochester, New Hampshire.
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Trump chuckled and interrupted him to say "We need this question. This is the first question."
"Anyway, we have training camps growing where they want to kill us," the man resumed. "That's my question: When can we get rid of them?
"We're going to be looking at a lot of different things," Trump responded.
"A lot of people are saying that, and a lot of people are saying that bad things are happening out there."
Trump moved on to another questioner, without addressing the man's assertions that President Barack Obama is a Muslim and not American.
In 2011, Trump repeatedly called into question Obama's citizenship and demanded the president release his birth certificate to prove that he was not born in Kenya, as many in the fringe "birther" movement suspect.
Obama, who was born in Hawaii, released the document, but Trump continued to express skepticism about it.
Thursday's exchange prompted outrage from Democrats and demands for an apology.
Democratic front-runner Hillary Clinton tweeted that Trump's failure to denounce the "hateful rhetoric about Muslims is disturbing, & just plain wrong. Cut it out."
Democratic Party chairwoman Debbie Wasserman Schultz, a congresswoman from Florida, blasted the Trump incident as "horrendous but unfortunately unsurprising," and called on other Republicans to repudiate the remarks.
Bernie Sanders, the liberal US senator challenging Clinton for the Democratic nomination, demanded that Trump "apologize to the president and American people for continuing the lie that the president is not an American and not a Christian."
The Trump incident recalls a notable moment on the 2008 campaign trail when Republican nominee John McCain was confronted by a supporter who told him that Obama was "an Arab."
"No ma'am. He's a decent family man and citizen who I just happen to have disagreements with on fundamental issues, and that's what this campaign is all about," McCain said, taking the microphone away from the questioner.