A senior al-Shabab commander who masterminded a wave of suicide attacks by the armed group has been killed in a US missile strike, two Somali security officials said.
Both sources and a Somali government spokesman named the target as Ahmed Mohamed Amey, a chemicals expert also known as Isku Dhuuq, Reuters news agency reported.
The intelligence officials said Amey was killed alongside his driver on Sunday.
A US official said the missile strike occurred in a remote area near Barawe, a coastal rebel enclave that was the site of a failed raid by American commandos in October targeting a fighter known as Ikrima. It was not clear if the missile was launched from a drone.
The security sources said Amey was close to al-Shabab leader Ahmed Abdi Godane, who since taking charge in 2008 has restyled the group as a global player in the al-Qaeda franchise - a transformation that was highlighted when it killed at least 67 people in an attack on a Kenyan shopping mall in September.
One of the officials, a former Islamist fighter who defected in 2009, said Amey advised Godane on the operations of al-Shabab's Amniyat "secret service", an elite unit blamed for suicide attacks in the Somali capital, Mogadishu.
"He was a good friend of Godane and the two were always on good terms," said the intelligence official, who identified himself as Hussein.
"He was the adviser of al-Shabab leader Godane on matters regarding the Amniyat and masterminding suicide bomb attacks."
The second intelligence source said Amey became an adviser to Godane, who hails from the same Dir clan, after another of the leader's top lieutenants, known as al-Afghani, was killed last year.
A Somali government spokesman described Amey as a "top leader of al-Shabab". A spokesman for the US embassy to Somalia, which is based in Nairobi, the Kenyan capital, could not be reached.
An offensive by African Union troops has driven al-Shabab from southern Somalia's major towns but the fighters still control large rural areas and remain the biggest security threat to east Africa, diplomats and analysts say.
Late last year, the US military deepened its involvement in Somalia, sending a handful of officers to Mogadishu to help advise and support Somali forces and AU troops, who have been battling al-Shabab since 2007.