Senior Al Shabab leader Adan Garar was killed in a drone strike last Friday, the Pentagon confirmed.
Mr Gara, who was a key suspect in the attack on Nairobi’s Westgate mall in 2013, was targeted with Hellfire missiles in southern Somalia.
The US defence department said in a statement that Garar's death "has dealt another significant blow to the Al Shabab terrorist organisation in Somalia".
Rear Admiral John Kirby, the Pentagon press secretary, said in a note on Twitter the department could now "confirm that Tahliil Abdishakur, chief of al Shabaab's intelligence and security wing, was killed in a U.S. air strike in Somalia on 29 December."