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Three Americans were killed when militants attacked a military base used by U.S. troops in Kenya early Sunday, the U.S. military said.

A predawn attempt by al-Shabab forces to breach security at Manda Bay Airfield was repelled, U.S. Africa Command said in a statement, but one U.S. service member and two contractors with the Defense Department were killed. Two other defense employees were wounded and were listed as stable.

The command said initial reports reflected damage to infrastructure and equipment, while an assessment was underway to determine whether any further damage was inflicted.

"Working alongside our Kenyan partners, the airfield is cleared and still in the process of being fully secured," it said.

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Al-Shabab, an Al Qaeda-linked group, claimed it had inflicted casualties and destroyed U.S. military equipment, including aircraft, in the raid on the military base near Kenya's border with Somalia.

NBC News has not verified the claims.

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Al-Shabab, based in neighboring Somalia, has launched a number of attacks in Kenya. It has also been the target of a growing number of U.S. airstrikes during President Donald Trump's administration.

The attack comes just over a week after an al-Shabab truck bomb in Somalia's capital, Mogadishu, killed at least 79 people and U.S. airstrikes killed several al-Shabab fighters in response.

Another U.S. airstrike Friday killed three militants, U.S. Africa Command said.

The base, established more than a decade ago, has fewer than 100 U.S. personnel, according to Pentagon figures.

A U.S. flag-raising there in August signaled its change "from tactical to enduring operations," the Air Force said at the time.