It said "several militants" were killed in the strike 60 miles northwest of the capital, Mogadishu, on Tuesday at about 1500 GMT. It was coordinated with the Somali government, AfriCom said in a statement.
"Al Shabaab has publicly committed to planning and conducting attacks against the US and our partners in the region," AfriCom said.
Earlier this month, the US warned of a threat to its diplomatic staff in Mogadishu and directed all non-essential staff to leave the capital.
Al Shabaab was pushed out of Mogadishu in 2011 and has lost control of most of Somalia's cities and towns. But the group retains a strong presence in the south and centre and can still carry out major attacks. It was blamed for bombings in Mogadishu last month that killed more than 350 people.
The group aims to topple Somalia's government, drive out African Union peacekeeping troops and impose its own harsh interpretation of Islamic law.
Al Shabaab retains a strong presence in the south and centre of Somalia
The United States military has carried out an air strike in Somalia against al Shabaab, an al Qaeda-linked Islamist insurgency that wants to topple the UN-backed government, the US Africa Command said on Wednesday.
