A U.S. military drone strike that targeted an international militant in southern Somalia killed four al-Shabab fighters, officials said Friday.

A U.S. official in Washington confirmed the attack was carried out by a U.S. drone. A second U.S. official said an "international" member of al-Shabab was the target of the strike, though he said a white Kenyan reported killed in the attack was not the target.

Both officials spoke on condition of anonymity in order to share details of the classified program.

Somalia's al-Shabab formally merged with Al Qaeda this month, a move analysts said was borne of desperation. Al-Shabab has been forced out of Mogadishu and faces military attacks on three sides. Al-Qaeda's power has ebbed as the group has seen key leaders killed in targeted attacks.

Still, al-Shabab boasts hundreds of foreign fighters -- many of whom have fighting experience in Iraq and Afghanistan -- among its ranks. The group also counts several dozen Americans, many of Somali origin, among its estimated 8,000 fighters.

Officials in Somalia confirmed Friday's attack in the Lower Shabelle region, where al-Shabab still controls wide swaths of territory. A Somali military official said a white Kenyan commander named Akram was among the four killed. The official said he could not be named for security reasons. A second Somali intelligence official confirmed the attack, but also could not be named.

The U.S. military has carried out multiple attacks inside Somalia against high-ranking militant targets in recent years.

Last month, a raid by Navy SEALs rescued an American and a Danish hostage from a gang of criminals. The U.S. military actions in Somalia are representative of the Obama administration's pledge to build a smaller, more agile military force that can carry out surgical counterterrorist strikes to cripple an enemy.

Kenya's military has also launched multiple airborne attacks in southern Somalia since Kenyan troops moved into the region in October.