Security warning traced to Syria unrest
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The move to tighten security measures at international airports with direct flights to the U.S. was partially motivated by concerns emanating from the civil war in Syria, Homeland Security Secretary Jeh Johnson said.

“We in national security are very concerned about the foreign fighter flow going into Syria, in particular from the United States, from European countries, other countries,” Johnson said during an interview Wednesday with MSNBC. “And we’re tracking that population. And we’re very concerned about it because there are extremists within the borders of Syria that would like to indoctrinate these people and send them back to their own countries with a different purpose.”

Earlier Wednesday, Johnson announced that he had directed the Transportation Security Administration to “implement enhanced security measures in the coming days” and said his department was reevaluating “the measures we take to promote aviation security.”

But Johnson did not explicitly say the new measures, which come as Americans ramp up travel ahead of the July 4 holiday, were related to concerns with Sunni extremists fighting within Iraq and Afghanistan.

But in his interview, Johnson conceded the government was “having to spend a lot of time tracking” Western individuals who entered Syria, out of concern they could become radicalized and return to Western Europe or the United States.

“We spend a lot of time talking to our foreign allies about the same problem,” he said. “They’re concerned about it as well.”

Still, Johnson encouraged Americans not to “overreact to it or over-speculate about what’s going on,” despite a “fair amount” of lingering concern over aviation safety.

“We continually evaluate the world situation and we not infrequently make changes to aviation security,” he said. “We either step it up or we feel sometimes we’re in a position to dial it back and so this is something that happens periodically.”

The U.S. Embassy in Uganda warned Americans in the country that it received information about a specific terror threat to the Entebbe International Airport on Thursday night.

The information came from the Uganda police force about an "unknown terrorist group," according to the embassy in the capital of Kampala, about 20 miles from Entebbe.

—Mario Trujillo contributed to this report.