MOGADISHU, Somalia, June 30 (UPI) -- An unmanned aircraft attacked two leaders of a militant Somali group with ties al-Qaida apparently wounding the targets, a U.S. military official said.

The drone strike occurred last week against senior members of al-Shabaab, coming as concern grows within the U.S. government that some leaders of the Islamist group are working more closely with al-Qaida to strike targets outside of Somalia, The Washington Post reported Thursday.

Somalia is at least the sixth country in which the United States is using drones to conduct airstrikes, the Post reported, joining Afghanistan, Pakistan, Libya, Iraq and Yemen.

A U.S. official said intelligence has been picked up in recent months that senior members of al-Shabaab have expanded their ambitions beyond attacks in Somalia.

"They have become somewhat emboldened of late, and, as a result, we have become more focused on inhibiting their activities," the official said."They were planning operations outside of Somalia."

Both of the leaders targeted in the drone attack had "direct ties" to American-born cleric Anwar al-Awlaki, the military official said.