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On "Fox and Friends" this morning, Donald Trump reacted to the terror attacks that rocked the Brussels airport and subway system Tuesday morning, killing at least 31 and injuring dozens.

Trump said the "absolutely horrible" attacks reinforce how important it is to make sure our border is secure and we vet anyone who enters the U.S.

He explained that tragedies like this and what happened in Paris in November seem to be becoming more and more frequent.

"We have a worldwide situation that is out of control," Trump said, adding that he fears this is just the beginning.

He said that's why he's renewing his call to "close up our borders" and put a stop to refugees from the Middle East entering the U.S.

"It’s going to get worse and worse, because we are foolish, we are foolish ... We can’t allow these people, at this point, to come into the U.S."

See more reaction from the Republican presidential front-runner above.

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