One US service member and two Department of Defense contractors were killed Sunday in an attack by the African militant group al-Shabab at an airfield in Kenya, US Africa Command announced in a statement.

Two Department of Defense employees were also injured in the attack. They are in stable condition and being evacuated, US Africa Command said. The agency said it would not be revealing the names of the victims yet.

Al-Shabab, headquartered in Somalia, claimed responsibility for the attack on the Manda Bay Airfield in Lamu county, which is near the Somali border, Reuters reported. The base is used by both US and Kenyan forces.

US Africa Command confirmed the attack in a statement.

The attack involved "indirect and small-arms fire," US Africa Command said. The militants initially breached the compound's borders but were repelled by Kenya Defence Forces and US Africa Command.

Reuters reported that five militants were killed in the defense and that a Kenyan military official said the base had been secured.

Six contractor-operated civilian aircraft were damaged in the attack as well, US Africa Command said.

"Our thoughts and prayers are with the families and friends of our teammates who lost their lives today," Stephen Townsend, the US Army general who is the commander of US Africa Command, said. "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 US interests."

Al-Shabab has ties to Al Qaeda and has carried out attacks in and around Somalia.

The group recently claimed responsibility for a bombing that killed about 80 people in Somalia's capital, Mogadishu, on December 28. It was one of the deadliest attacks in the country in more than two years.