SEALs went after a commander named Ikrima, a Kenyan of Somali origin, who was linked to two now-dead al-Qaida operatives known to have played roles in the embassy bombing as well as the 2002 attacks on a hotel and airline in Mombasa.
Ikrima was also believed to be involved in a number of foiled plots between 2011 and 2013, including one on an airport in northeastern Kenya.
The raid was conducted by members of the elite SEAL Team Six, the same unit that conducted the Pakistan operation that killed Osama bin Laden in 2011.
SEALs entered the the port city of Barawe in the early hours of Saturday morning, targeting a coastal villa owned by al-Shabaab leader Mukhtar Abu Zubayr. A heavy firefight broke out after the SEALs landed on the beach, and they made a "prudent decision" to withdraw, without knowing if they had killed their target, a senior U.S. official said.
Ikrima was believed to do much of the Kenyan recruiting and training for al-Shabaab, the terrorist organization that works closely with al-Qaida and has a stated goal of transforming Somalia into a fundamentalist Islamist state.
The group took credit for last month's attacks on the Westgate mall in Nairobi that left at least 67 people dead. In 2009, it led a bloody campaign to take control of the Somalian capital city of Mogadishu, at times occupying most of the city, and in 2010, suicide bombers attacked crowds watching the World Cup in Kampala, Uganda, killing 74 people.
Sunday's raid in Somalia was one of two carried out by U.S. forces Saturday. The other, in Tripoli, Libya, netted wanted terrorist Abu Anas al Libi. Al Libi, who was captured by U.S. Army Delta Force members and taken to a Navy ship for interrogation, has been indicted for his alleged involvement in the planning of the Nairobi embassy attack.