(NBC) - The man whisked off the streets of Tripoli, Libya, Saturday was among the top remaining leaders of al Qaeda, an elusive confidant of Osama bin Laden, as well as an alleged conspirator in the 1998 East Africa embassy bombings.
Anas al Libi, whose real name is Nazih Abdul-Hamed Nabih al-Ruqai'I, has over the years been reported as killed, captured or living in Iran.
But the U.S. has known he's been back in his native Libya for more than two years, the latest stop on a journey that has taken him from Tripoli to Sudan, where he met bin Laden, to England, Kenya, Afghanistan and Iran.
He returned to Libya in the dying days of the regime of former leader Moammar Gadhafi. He even lost his son in the civil war that led to Gadhafi's ouster and death.
On Saturday, the Pentagon confirmed al Libi had been captured.
"As the result of a U.S. counterterrorism operation, Abu Anas al Libi is currently lawfully detained by the U.S. military in a secure location outside of Libya," said Pentagon spokesman George Little.
In another statement Sunday morning, Little said al Libi was being held under the "law of war."
Libya's Prime Minister Ali Zeidan earlier on Sunday had asked U.S. authorities to "explain" the raid.
"The Libyan government is following the news of the kidnapping of a Libyan citizen who is wanted by U.S. authorities," Zeidan's office said in a statement. "The Libyan government has contacted to U.S. authorities to ask them to provide an explanation."
In the days after 9/11, al Libi was among the first names placed in the Federal Bureau of Investigation's Most Wanted Terrorists list with a reward of $25 million – the same amount attached to bin Laden and other senior officers of al Qaeda. It was later reduced to $5 million, but the United States' desire to bring him to justice never waned.
"He's one of the last guys from the East Africa embassy bombings who was still out there," said a senior U.S. intelligence official Saturday night.
"We still wanted him," added a second official, indicating that the Aug. 7, 1998, attacks on U.S. Embassies in Dar es Salaam, Tanzania, and Nairobi, Kenya, remained a high priority in the U.S. government.
"Symbolically, the embassy bombings are for the U.S. what Munich was for the Israelis. It's about closure," said Karen Greenberg, director for the Center on National Security at Fordham University Law School.
Of the 21 people indicted in the embassy bombings case by the U.S. Justice Department, eight have been killed, including bin Laden, one died awaiting trial, and another eight are in jail, either convicted or awaiting trial. Al Libi was one of four fugitives until Saturday.
The U.S. carried out twin campaigns in Somalia and Libya where it captured a senior al Qaeda official. NBC's Jim Miklaszewski reports.
"He is significant both historically – a key operator in advancing the 1998 attacks – and currently given his presence in Libya, combined with deep and longstanding relations with core al Qaeda leadership," said Michael Leiter, former director of the National Counter-Terrorism Center and an NBC News consultant.
Al Libi was born either on March 30 or May 14, 1964, making him 49 years old. Well-educated, like many in the al Qaeda hierarchy in its early days, he speaks English as well as Arabic and studied computer and nuclear science at the University of Tripoli before joining the jihad. His fundamentalist beliefs drew the attention of Gadhafi's security forces, and he began a life on the run.
By 1994, he had joined bin Laden in Sudan, where the al Qaeda leader had settled after the end of the Soviet occupation of Afghanistan. Tall and angular like bin Laden, he was well-known in the organization and initially seen as a favorite of bin Laden.
He allegedly was a key player in the planning of the East Africa embassy bombings, which killed 12 Americans and more than 200 Kenyans and Tanzanians in Nairobi and Dar Es Salaam, the Tanzanian capital. According to one of the co-conspirators who later cooperated with U.S. law enforcement, al Libi discussed bombing the U.S. embassy with him years before the attack was carried out and participated in the surveillance of the embassy and the attack planning.
The co-conspirator, Ali Mohamed, also said al Libi had surveyed the British, French and Israeli embassies in Nairobi. Nairobi was ultimately chosen, according to reports, because it was the home of the regional Central Intelligence Agency station that tracked bin Laden in Sudan.
Al Libi was not in Nairobi when the bombings took place, having returned to London in 1995. He successfully sought asylum in the United Kingdom, as did many of those who formed al Qaeda's British encampment that operated openly. The group even formed a public company whose incorporation papers were signed by bin Laden.
After the bombings, however, British authorities became interested in the group, arresting several at the request of the United States. In 1999, authorities questioned al Libi about his connections.
Ali Soufan, an FBI agent and al Qaeda expert, described in his book, "The Black Banners: The Inside Story of 9/11 and the War Against al-Qaeda," how he was called to Britain after Scotland Yard tracked down al Libi and placed him in custody. Al Libi was ultimately released because he had cleared his hard drive and British police believed they had no evidence to hold him, Soufan wrote.
By 2000, after the U.S. had turned Ali Mohamed, al Libi was indicted. But by the time Manchester Metropolitan Police arrived at his apartment in the Midlands city, he was nowhere to be found.
Al Libi "evaded the team that was sent to follow him. We didn't know where he had disappeared to but we were pretty certain he was on his way to Afghanistan," Soufan wrote.
However, on a laptop left behind, police found a document that would become essential in the fight against al Qaeda: "Military Studies in the Jihad against Tyrants," a manual that included chapters on car bombings, sabotage, torture and disguises. It was later used in the trials of other co-conspirators in the 2001 embassy bombing trials.
Al Libi has been reported captured on several occasions, including by U.S. forces in 2002 during an assault on the caves of Tora Bora in eastern Afghanistan, and then in Sudan later in 2002. Some human rights groups have used those reports to allege that he has been held in a secret CIA prison, but the U.S. has denied it and his name was never removed from the Most Wanted Terrorists list.
One problem U.S. prosecutors may have if al Libi is brought back to the United States is that testimony from other co-conspirators in the 2001 trial suggests he had reportedly argued with bin Laden over financial matters. It's also unknown what role, if any, al Libi currently has in al Qaeda.