US Navy SEALReuters

U.S. Navy SEAL Team Six pulled out during a raid in Somalia to capture suspected Al-Shabaab leader Ikrima when it became clear that he couldn't be taken alive, a senior U.S. official told CNN.

"Their mission was to capture him. Once it became clear we were not going to (be) able to take him, the Navy commander made the decision to withdraw," said the official, who has direct knowledge of the entire operation but declined to be identified publicly.

The mission's aim of capturing Ikrima, rather than killing him, is why the method of attack was preferred to a drone strike on the guarded seaside villa, the official said.

Another U.S. official told CNN the Navy SEALs reported seeing children at the compound, and that this was part of the reason the mission was stopped.

The Pentagon is disputing the suggestion that Al-Shabaab drove out the SEALs.

"That's not how it happened," Pentagon spokesman George Little insisted to CNN.

"There was a firefight, absolutely, and they took every step to avoid civilian casualties in this case, and that's what our military personnel do. They weigh these kinds of decisions and they made a prudent decision on the ground to depart. It was their decision."

Citing military sources, NBC reported that the SEALs arrived at the compound and identified Ikrima before being spotted by an al-Shabab “fighter. That fighter called in others and began firing, putting the special operations team under siege. The Seal Team withdrew back to the beach in part because it believed a sustained firefight would endanger a group of nearby children,” according to NBC.