A U.S. service member and two Defense Department contractors were killed Sunday in an attack by an al Qaeda-linked group on a military base in Kenya used by American forces, a Pentagon spokesman confirmed. Witnesses told BBC News they heard gunfire and saw plumes of black smoke emerge from Camp Simba in the Lamu region of Kenya.

The U.S. Africa Command blamed al Shabaab, al Qaeda's outpost in Africa, for the attack. The names of the dead are being withheld pending family notification.

"Our thoughts and prayers are with the families and friends of our teammates who lost their lives today," said U.S. Army General Stephen Townsend, commander of the U.S. Africa Command, in a statement. "As we honor their sacrifice, let's also harden our resolve. Alongside our African and international partners, we will pursue those responsible for this attack and al Shabaab who seeks to harm Americans and U.S. interests. We remain committed to preventing al Shabaab from maintaining a safe haven to plan deadly attacks against the U.S. homeland, East African, and international partners."

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The Kenyan Defense Forces told BBC News that "an attempt was made to breach security at Manda Air Strip" before being thwarted. Five militants were killed, according to the Kenyan Defense Forces.

The U.S. Africa Command said the situation remained "fluid," although Kenyan authorities told BBC News the insurgents had been driven out of the base.

According to The Associated Press, two fixed-wing aircraft, a U.S. Cessna and a Kenyan one, were destroyed along with two U.S. helicopters and multiple U.S. vehicles. The U.S. military said only that "initial reports reflect damage to infrastructure and equipment."

BBC World Service Africa editor Will Ross called the attack an "audacious pre-dawn raid" by al Shabaab. Lamu is a popular tourist destination.

The attack comes just over a week after at least 78 people were killed when a truck bomb exploded at a checkpoint in Somalia's capital, Mogadishu. Al Shabaab was also blamed for that attack.