Abdel Basset Ali al-Megrahi, a shadowy Libyan intelligence officer who was convicted in the 1988 bombing of Pan Am Flight 103 over Lockerbie, Scotland, that killed 270 people, and whose release from prison in 2009 sparked international uproar, died May 20 at his home in Tripoli. He was 60.

The death was confirmed by his son, Khaled al-Megrahi, the Associated Press reported.

Tommy Vietor, a spokesman for the National Security Council, wrote in a e-mail, “Megrahi’s death concludes an unfortunate chapter following his release from prison in 2009 on medical grounds — a move we strongly opposed. As we have long said, we want to see justice for the victims of the Lockerbie bombing and their families. We will continue working with our new partners in Libya toward a full accounting of Qadhafi’s horrific acts.”

Mr. Megrahi was serving a life sentence in a Scottish prison in 2008 when he was diagnosed with prostate cancer. In August 2009, he was released under a Scottish law that allows terminally ill prisoners to die at home. When he was freed, Mr. Megrahi was expected to live three months.

That Mr. Megrahi died in his native country — and not in a Scottish prison cell — was a shocking end to the life of a man considered a terrorist by the U.S. government and whom the FBI once placed on its “most wanted” list.

During the late 1980s, Mr. Megrahi technically was serving as chief of security for the state-owned Libyan Arab Airlines. In reality, however, the job was his cover as a clandestine officer in the Jamahiriya Security Organization, Libya’s intelligence branch.

His work with the airline took him around the world, including to Switzerland and the Mediterranean island nation of Malta. It also helped him gain intimate knowledge of airport security — and its weaknesses.

On Dec. 21, 1988, a bronze hard-shell Samsonite suitcase was loaded onto an Air Malta plane bound for Frankfurt. From Germany, the suitcase was transferred onto a flight to London. Upon arrival, the bag was placed inside the forward cargo bay of a Boeing 747 jumbo jet.

Bound for New York, Pan Am Flight 103 held 189 Americans, including a group of Syracuse University college students returning home for the holidays from a semester abroad.

The jet was cruising at 31,000 feet at 7:03 p.m. when a bomb hidden inside the Samsonite bag exploded. All 259 aboard died, and 11 people on the ground were killed when flaming chunks of the plane plummeted into the bucolic village of Lockerbie.

The spectacular act of terrorism led to a manhunt in which an international team of investigators pursued leads in 50 countries and interviewed 14,000 people.

Georgetown University terrorism expert Bruce Hoffman said in an interview in April that it was “at the time the largest criminal investigation in the history of the FBI.”

At first, Mr. Megrahi escaped suspicion. Hoffman said a critical factor in linking Mr. Megrahi to the bombing was the fact that the plane had been delayed before takeoff. Had Pan Am 103 left on time, the plane would have gone down somewhere over the Atlantic, Hoffman said, making the recovery of crucial evidence a nearly impossible task.

Authorities traced Mr. Megrahi to the crime after combing through an 845-square-mile area of Scotland in a search for clues in the wreckage.The break in the case came after investigators discovered a plastic fragment the size of a fingernail and the singed remains of a shirt amid the debris.

The shard of green plastic proved to be the circuitry of a Swiss-made timing device used to detonate the explosive. U.S. intelligence analysts later found that the Libyan government had purchased an identical set of timers earlier in the 1980s.

The shirt, which authorities found had been packed inside the same suitcase as the bomb, was sold at a Maltese fashion boutique called Mary’s House. The shop owner later identified Mr. Megrahi as the person who had bought the shirt.

The complexity of the operation, which required expert knowledge of airport security to smuggle on a piece of luggage unnoticed, and the fact that the bomb’s timer was linked to Libyan intelligence led to Mr. Megrahi’s indictment in 1991.

“The indictment, based on very firm forensic evidence, clearly and incontrovertibly pointed a spotlight on a blatant act of state-sponsored terrorism and implicated two Libyan agents acting in its commission,” Hoffman said.

During the 1990s, the FBI described Mr. Megrahi as an at-large fugitive who was “armed and extremely dangerous.” A $4 million bounty was placed on his head.

Charges were filed simultaneously against Mr. Megrahi and a Libyan co-conspirator, Lamen Khalifa Fhimah, in the United States and Scotland.

Libyan leader Moammar Gaddafi refused to extradite the men but placed them both under house arrest.

In response, the U.N. Security Council levied sanctions against Libya that hobbled the country’s economy. After lengthy negotiations led by South Africa’s president at the time, Nelson Mandela, and then-U.N. Secretary General Kofi Annan, Gaddafi agreed in 1999 to surrender the men to a trial in the Netherlands with Scottish judges.

In court proceedings, Mr. Megrahi and Fhimah pleaded not guilty. The prosecutorial team called 227 witnesses; the defense called three. Neither of the accused men testified on their own behalf.

In 2001, Mr. Megrahi was convicted of mass murder and sentenced to life in prison, with a minimum term of 27 years. Fhimah was acquitted.

Gaddafi’s government never denied involvement in the bombing and over several years paid $2.7 billion to the families of victims.

After his cancer diagnosis, Mr. Megrahi requested that he be sent home. When he arrived in Tripoli in 2009, he was greeted by hundreds of jubilant Libyans, including some who wore shirts depicting his face. Others in the crowd waved Scottish flags, an apparently taunting gesture.

He earned a reputation as a national hero, and babies were reportedly named after him. He was granted an exclusive audience with Gaddafi.

The decision to allow his release enraged many of the families of Lockerbie bombing victims. President Obama called Mr. Megrahi’s release “a mistake.”

Abdel Basset Ali al-Megrahi was born April 1, 1952, in Tripoli. He studied in the United States during the 1970s and spoke fluent English. He received an engineering degree from Benghazi University in Libya.

Survivors include his wife, Aisha, and five children.

At home in Libya for the past two years, Mr. Megrahi lived in a resplendent villa in Tripoli, complete with a garden and swimming pool.

Until his death, Mr. Megrahi maintained his innocence, claiming that he was the victim of an international conspiracy.

“You judge me falsely,” Mr. Megrahi once told an American interviewer. “My life is clean.”