The strike occurred about 65 kilometers (40 miles) southwest of Mogadishu and comes after as many as 512 people were killed in a massive truck bombing in October.
"In coordination with the Federal Government of Somalia, US forces conducted an air strike against an al-Shabaab vehicle-borne improvised explosive device in the early morning hours of December 12," the US military's Africa Command said in a statement."This strike supports our partner forces by removing an imminent threat to the people of Mogadishu."
AFRICOM added that it had assessed that no civilians were killed in the strike.
The Shabaab has been fighting to overthrow successive internationally backed governments in Mogadishu since 2007 and frequently deploys car and truck bombs against military, government and civilian targets.
The devastating October blast leveled buildings in the capital's busy Kilometer 5 neighborhood.
Since then the United States -- which supports Somalia's fledgling army as well as carrying out its own operations against the Shabaab and a separate self-proclaimed Islamic State group in the north of the country -- has increased the frequency of air strikes targeting jihadist leaders.