Ahmed Abu Khatallah was taken into custody by U.S. Special Operations Sunday near Benghazi and is being held in a "secure location outside Libya."
Pentagon press secretary Rear Adm. John Kirby confirmed Khatallah's capture and said there were no civilian or U.S. personnel casualties during the raid, adding that all members of the Special Operations team had safely left Libya.
Khatallah is reportedly being transported by ship to the United States, and is expected to be arraigned in Washington, D.C., although officials would not say when he was expected to arrive.
The Obama administration celebrated the news Tuesday, calling it "an important milestone."
White House press secretary Jay Carney said Khatallah was "a key figure in the attack," but said the investigation wasn't over.
"With this operation, the United States has once again demonstrated that we will do whatever it takes to see that justice is done when people harm Americans," President Obama said in a statement. "We will continue our efforts to bring to justice those who were responsible for the Benghazi attacks."
Republican lawmakers, who have accused the administration of hiding information related to its response to the Sept. 11, 2012 attack, said they were pleased to hear of Khatallah's capture but skeptical of plans to arraign him in Washington.
"Rather than rushing to read him his Miranda rights and telling him that he has the right to remain silent, I hope the administration will focus on collecting the intelligence necessary to prevent future attacks and to find other terrorists responsible for the Benghazi attacks," said Sen. Kelly Ayotte, R-N.H., in a statement.
And Sen. John McCain, R-Ariz., said he should not be brought to U.S. soil, but instead taken to Guantanamo.
"That's where we put terrorists when we apprehend them," McCain said.
The news of Khatallah's capture will likely undercut a frequent Republican criticism that the administration has not done enough to pursue those responsible for the attacks that led to the deaths of Ambassador Chris Stevens and three other Americans. A spokeswoman for Rep. Trey Gowdy, R-S.C., the chairman of a select committee formed to investigate the attacks and the administration's response to them, declined to comment.
"This operation demonstrates that when America says it will bring to justice those who attack our country or our people, we will back up that solemn commitment with strong action -- regardless of political party," said Rep. Elijah Cummings, D-Md., the ranking member on the Benghazi committee who has dismissed much of the Republican-led investigation as a witch hunt.
Attorney General Eric Holder promised "any effort necessary" in the prosecution of Khatallah.
"Khatallah currently faces criminal charges on three counts, and we retain the option of adding additional charges in the coming days," Holder said. "Even as we begin the process of putting Khatallah on trial and seeking his conviction before a jury, our investigation will remain ongoing as we work to identify and arrest any co-conspirators."
Very pleased our Special Forces have detained Ahmed Abu Khattala. #Benghazi— Lindsey Graham (@GrahamBlog) June 17, 2014
The raid and Khatallah's capture were first reported by the Washington Post Tuesday.