Story highlights Trump also said it's time to start surveillance of mosques, and said the U.S. should shut some down if they have radical leaders.

The mogul slammed German Chancellor Angela Merkel, one of the most powerful leaders in Europe, saying she "blew it"

Washington (CNN) Donald Trump says he's now more against allowing Syrian refugees into the U.S. than ever, warning it could be a way for terrorists to sneak into the country.

"We have no idea who these people are, we are the worst when it comes to paperwork," Trump said Monday on CNBC. "This could be one of the great Trojan horses."

Trump has been saying for weeks on the campaign trail that the U.S. should not accept refugees from the civil war torn country, and he says he's only standing by that position stronger in the wake of the horrific terrorist attacks in Paris.

At least six of the suspects in the Paris attack have ties to Syria, according to French affiliate BFM, and at least one is believed to have entered Europe with refugees.

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