The U.S. Africa Command said the airstrike occurred near Jilib in the Middle Juba region.
There were no reports of Americans killed or wounded. The U.S. statement did not say whether any Somali forces were killed or wounded by the al-Qaida-linked extremists.
Al-Shabab via its Shahada news agency asserted that its attack on two Somali army bases killed at least 41 soldiers. It described the location as the Bar Sanjuni area near the port city of Kismayo.
There was no immediate comment from Somalia’s government.
In neighboring Ethiopia, state television cited the defense ministry as saying more than 60 al-Shabab fighters had been killed and that four vehicles loaded with explosives had been “destroyed.” Ethiopia contributes troops to a multinational African Union peacekeeping mission in Somalia and has troops there independently under Ethiopian army command.
A Somali intelligence officer said al-Shabab had been amassing fighters for more than a week to launch a major attack against Somali and Kenyan forces in order to disrupt a planned offensive against the extremists. The officer said some 400 extremists, including foreign ones, had been prepared, including two suicide car bombers. The officer spoke on condition of anonymity because they were not authorized to speak to reporters.
Al-Shabab controls large parts of rural southern and central Somalia and continues to carry out high-profile suicide bombings and other attacks in the capital, Mogadishu, and elsewhere.
The Islamic extremist group claimed responsibility for the deadly attack on a luxury hotel complex in the capital of neighboring Kenya on Tuesday, the latest high-toll assault inside that county in retaliation for Kenya sending troops to Somalia to fight al-Shabab.
The extremist group finds itself under pressure at home on a number of fronts, including from a small presence of rival fighters linked to the Islamic State organization, which has begun challenging al-Shabab in recent months.
The United States has dramatically stepped up airstrikes against al-Shabab in Somalia since President Donald Trump took office, carrying out at least 47 such strikes last year. Some have targeted top al-Shabab leaders or key financial officials; the extremist group funds its attacks with an extensive network of “taxation” and extortion.
In October, the U.S. said an airstrike killed about 60 fighters near the al-Shabab-controlled community of Harardere in Mudug province in the central part of the country.
The airstrikes hamper the extremist group but have not “seriously degraded al-Shabab’s capability to mount strikes either inside or outside Somalia,” Matt Bryden of Sahan Research, an expert on the extremists, told The Associated Press after the Nairobi hotel attack.
Airstrikes alone cannot defeat the extremists, Bryden said, and must be combined with more ground-based attacks as well as a non-military campaign to win over residents of extremist-held areas.
The U.S. on Saturday said it is committed to “preventing al-Shabab from taking advantage of safe havens from which they can build capacity and attack the people of Somalia.”