US commandos have captured the suspected ringleader of the deadly 2012 attack on an American compound in Benghazi, in a raid hailed by the White House as a triumph for "justice."
Special forces, working with FBI agents, carried out Sunday's operation and the suspect, Ahmed Abu Khatallah, was en route to the United States, where he will face criminal charges, officials said.
The raid represented a victory for President Barack Obama who has faced intense criticism over his administration's handling of the September 11, 2012 Benghazi assault and its aftermath.
"The United States has an unwavering commitment to bring to justice those responsible for harming Americans," Obama said.
"Since the deadly attacks on our facilities in Benghazi, I have made it a priority to find and bring to justice those responsible for the deaths of four brave Americans."
Attorney General Eric Holder said the raid showed "our nation's memory is long and our reach is far."
There were no civilian casualties in the action and the suspect was in US custody at a "secure location outside of Libya," Pentagon spokesman Rear Admiral John Kirby said.
All US troops and personnel taking part in the operation have "safely departed Libya," he added.
Top US diplomat John Kerry called the raid a "bold action" that served as reminder that there was no "impunity" for militants trying to harm America.
The hours-long assault on US facilities in Benghazi in 2012, which also targeted a CIA outpost, killed the US ambassador to Libya, Christopher Stevens, and three other Americans.
The attack shocked Washington and became a highly-charged political issue, raising questions about security at US missions. Former secretary of state Hillary Clinton faced hostile questioning before lawmakers over the issue.
Republican lawmakers alleged that the White House failed to respond decisively and then tried to hide some facts in the episode.
The Obama administration has accused critics of politicising a tragic event and that it has divulged all the details of the case.
US federal prosecutors have charged Khatallah with murder, carrying a weapon and offering material support to "terrorism," according to an indictment unsealed on Tuesday.
The charges reflect accounts from Libyan officials and witnesses who have singled out Khatallah as allegedly taking part in the assault that day.
"We have made it clear, since that cowardly attack on our facilities, that we would go at any length to find, apprehend, bring to judgment, those who perpetrated it," White House spokesman Jay Carney said.
"The capture of Ahmed Abu Khatallah is not the end of that effort but it marks an important milestone."
The State Department has identified Khatallah as a senior leader of Ansar al-Sharia, a Libyan Islamist group it brands a "terrorist" organization responsible for a spate of attacks and assassinations.
After similar raids, the military has held suspects aboard naval ships before flying them to the United States to face legal charges.
Senator Lindsey Graham indicated the suspect was being held on a ship and blasted the administration for not taking him to the US-run prison at Guantanamo Bay, Cuba.
He said in a tweet that he was "very pleased our Special Forces" captured Khatallah but he criticized the Obama administration for holding the suspect on a naval ship.
Holding Khatallah "on a ship shows the haphazard approach which comes from not having rational detention & interrogation policies," the senator wrote.