BRUSSELS (AP) — NATO's supreme commander says he's worried that boats attempting to carry migrants across the Mediterranean to southern Europe may also be ferrying criminals and potential terrorists.

U.S. Air Force Gen. Philip Breedlove on Thursday said, "we do not know what is in these migrations coming across the Mediterranean from northern Africa."

He told a news conference that he and other NATO officials are concerned about who might be on the often dangerously unseaworthy craft carrying passengers from Libya and other nations.

Breedlove said "some of these people are legitimate refugees from ungoverned spaces." But other passengers, the general said, "we believe are organized crime, and yes, we believe there could be elements of extremists" as well.

Breedlove spoke following a meeting of NATO's Military Committee in Brussels.