A Washington newspaper reports that a U.S. drone aircraft fired on two leaders of Somalia's al-Shabab militant group last week, apparently wounding them.

The Washington Post based its report on an unnamed senior military official familiar with the operation.

The official said the drone strike was carried out amid concerns that al-Shabab is working more closely with al-Qaida to launch attacks outside Somalia's borders.

Witnesses in Somalia reported the attack June 23, saying it took place in Qandal, a coastal area south of Kismayo.

Somalia's deputy defense minister, Abdirashid Mohamed Hiddig, later told VOA that the operation was carried out by a “friendly country.”

Hiddig described Qandal as a command-and-control center for al-Shabab. He said the group uses the site to store food, weapons and equipment for explosives.

This week, U.S. officials said the Pentagon is sending four drones to East Africa to help battle militants in Somalia.

Military officials say the defense department is sending the drones to Uganda and Burundi, whose forces make up the African Union peacekeeping force helping the Somali government.

Al-Shabab has been primarily active within Somalia, where it is fighting to overturn the transitional government and impose strict Islamic law. The group has also claimed responsibility for bombings in Uganda last July that killed more than 70 people.

Al-Shabab rules much of southern and central Somalia and part of the capital, Mogadishu. But a recent offensive by AU and Somali government forces has retaken parts of the capital.

The Washington Post says Somalia is the sixth country where the United States is using drones to conduct attacks. It identifies the others as Afghanistan, Pakistan, Libya, Iraq and Yemen.