The US military launched a missile strike in Somalia targeting a suspected al-Shabab militant leader, defence officials said.
One official said an unmanned drone launched the missile late on Sunday, but declined to confirm the suspect's identity or whether the strike was successful. The US government had "been tracking this guy for years", the official said.
A second US official said the strike in the southeastern port town of Barawe was against a senior al-Shabab commander.
"The US is assessing the results of the operation" to determine if the suspect was killed, the official added.
The US strike took place just a day after al-Shabab, which is linked to al-Qaeda, called for attacks against foreign forces after arch-enemy Ethiopia joined the African Union force battling the extremists.
Hardline al-Shabab insurgents control large parts of rural southern Somalia, and despite having been driven from a string of towns by the UN-backed mission known as AMISOM, guerilla units stage regular deadly attacks in the capital, Mogadishu.
The United States has sent a handful of military advisers to Somalia in recent months to help bolster an African Union force fighting extremist militants there.
The deployment marked the first stationing of US troops in the troubled country since 1993, when two Blackhawk helicopters were shot down and 18 Americans were killed.
Top al-Shabab commanders met this week after Ethiopia formally joined AMISOM, an al-Shabab spokesman said.