Hot on the heels of his suggestion that some mosques be closed over security concerns in the wake of terrorist attacks in Paris last week, Donald Trump says he would be open to requiring Muslims to register in a database and carry identification marking their religious beliefs.

"We're going to have to do things that we never did before," the GOP front-runner said in an interview with Yahoo News. "And some people are going to be upset about it, but I think that now everybody is feeling that security is going to rule. And certain things will be done that we never thought would happen in this country in terms of information and learning about the enemy. And so we're going to have to do certain things that were frankly unthinkable a year ago."

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In the wide-ranging Yahoo News interview, Trump said he wouldn't rule out the possibility of registering Muslim citizens in a database, citing an unprecedented need for heightened security measures in an age of indiscriminate terrorist activity.

"We're going to have to — we're going to have to look at a lot of things very closely," he said in response to Yahoo News' question. "We're going to have to look at the mosques. We're going to have to look very, very carefully."

The businessman received immediate backlash for entertaining the idea, which many compared to the tracking system used for Jewish citizens in Nazi Germany—an uncomfortably recent historical precedent. Trump also said he would not be opposed to warrantless searches of Muslim citizens. The candidate cited heightened concerns over the thousands of Syrian refugees slated to settle in the U.S. in coming years, referencing "radical Islamic terrorism," and the five Syrian men detained in Honduras this week with fake Greek passports. Honduran officials later confirmed the men were not linked to "any terrorist cell," and that they were university students seeking refuge in the U.S.

"Some people are going to be upset about it, but I think that now everybody is feeling that security is going to rule," he said, adding that any Syrian refugee taken in under the Obama administration would be deported.

"They're going to be gone. They will go back. ... I've said it before, in fact, and everyone hears what I say, including them, believe it or not," he said. "But if they're here, they have to go back, because we cannot take a chance. "You look at the migration, it's young, strong men. We cannot take a chance that the people coming over here are going to be ISIS-affiliated."