Ben Carson
Republican presidential candidate Ben Carson speaks during a campaign rally at the Henderson Pavilion on November 15, 2015 in Henderson, Nevada. Carson is battling Donald Trump for the lead in polls for the Republican presidential nomination.Ethan Miller/Getty Images

Republican presidential candidate Ben Carson referred to Syrian refugees as dogs on 19 November as he discussed the reported threat they pose to the US. Carson, who has made several disparaging comments against Muslims in the past, said authorities should be vigilant to screen out the "mad dogs" among refugees who may attempt to commit acts of terror.

"For instance, if there's a rabid dog running around in your neighbourhood, you're probably not going to assume something good about that dog, and you're probably going to put your children out of the way," Carson said. "It doesn't mean that you hate all dogs by any stretch of the imagination, but you're putting your intellect into motion."

The leading GOP candidate added: "We have to have in place screening mechanisms that allow us to determine who the mad dogs are, quite frankly. Who are the people who want to come in here and hurt us and want to destroy us?" Carson added that Americans should be in fear of a terrorist attack in the US because Islamic State (Isis) terrorists are "so much greater a threat to us" than al-Qaeda ever was.

"They weren't nearly as developed as they are now," he said of the "global jihadist movement". According to The Washington Post, Carson added the 9/11 attacks "really didn't require a great deal of sophistication because we were not paying attention, we were not coordinating our efforts. So you didn't have to be all that great. You had to be able to fly some planes and get a couple of people in here. That's going to be a lot more difficult now."

The Council on American-Islamic Relations called out Carson for his comments while also addressing fellow Republican Donald Trump, who said he would consider a national database of Muslims in the US or special identification cards for them.

"By mainstreaming Islamophobic and unconstitutional policies, Donald Trump and Ben Carson are contributing to an already toxic environment that may be difficult to correct once their political ambitions have been satisfied," said CAIR Government Affairs Manager Robert McCaw. "Such extremist rhetoric is unbecoming of anyone who seeks our nation's highest office and must be strongly repudiated by leaders from across the political spectrum."

Carson has been the centre of scrutiny for his apparent lack of knowledge when it comes to foreign policy. A recent New York Times report quoted adviser Duane Clarridge, a former CIA agent who said Carson was unable to fully grasp foreign policy issues. According to the Post, Carson attempted to distance himself from Clarridge, who he called "a consultant".