Abdelbaset al-Megrahi, the only person convicted over the 1988 Lockerbie bombing above Scotland which killed 270 people, has died at his home in the Libyan capital Tripoli.
Megrahi, 60, was convicted by a special court in the Netherlands in 2001.
He was released from prison in Scotland in 2009 on compassionate grounds. He was suffering from cancer and was said to have only months to live.
When he returned to the Libyan capital, he received a hero's welcome.
Shortly before being freed, Megrahi dropped his second appeal against his conviction.
His release sparked the fury of many of the relatives of the victims of the Lockerbie disaster.
But others believed he was not guilty of the bombing.
A spokesman for the families of the Lockerbie victims said Megrahi's death was to be "deeply regretted".
"As someone who attended the trial, I have never taken the view that Megrahi was guilty," David Ben-Ayreah said. "Megrahi is the 271st victim of Lockerbie."
Died at home
His brother Abdulhakim said on Sunday that Megrahi's health had deteriorated quickly and he died at home in Tripoli.
He told the AFP news agency that Megrahi died at 13:00 local time (11:00 GMT).
Last month, Megrahi's son said his father had been taken to hospital for blood transfusions.
Megrahi, who had cancer, died at his home in Tripoli, his brother said
Megrahi, a Libyan intelligence officer, always denied any responsibility for the bombing of Pan Am Flight 103 in December 1988.
It remains the deadliest terrorist incident ever to have taken place on British soil.
All 259 people aboard the plane, which was travelling from London to New York, were killed, along with 11 others on the ground.
Investigators tracing the origins of scraps of clothes wrapped around the bomb followed a trail to a shop in Malta which led them, eventually, to Megrahi.
He and another Libyan, Al Amin Khalifa Fhimah, were indicted by the Scottish and US courts in November 1991.
But Libya refused to extradite them. In 1999, after protracted negotiations, Libya handed the two men over for trial, under Scottish law but on neutral ground, the former US airbase at Camp Zeist in the Netherlands.
Their trial began in May 2000. Ffimah was acquitted of all charges, but Megrahi was found guilty and sentenced to a minimum of 27 years in prison.
He served the first part of his sentence at the maximum-security prison at Barlinnie, in Glasgow, but was transferred in 2005 to Greenock prison.
Last August after the fall of Libyan leader Col Muammar Gaddafi, Megrahi was reported to be "in and out of a coma" at his home in Tripoli.
There have been calls for him to be returned to jail in the UK or tried in the US.
But shortly after they toppled Colonel Gaddafi, Libyan rebel leaders said they would not extradite Megrahi or any other Libyan.
In his last interview, filmed in December 2011, Megrahi said: "I am an innocent man. I am about to die and I ask now to be left in peace with my family."
He had previously claimed he would release new information about the atrocity but little new has emerged.
Megrahi had rarely been seen since his return to Tripoli, but he was spotted on Libyan television at what appeared to be a pro-government rally in July 2011.
UK Foreign Secretary William Hague said the public appearance confirmed that a "great mistake" was made in releasing him from jail.
