So far today, Libya appeared to be keeping quiet about the anniversary.
Abdel Baset al-Megrahi was freed from prison in Scotland on Aug. 20, 2009, on compassionate grounds after he was diagnosed with prostate cancer, and doctors said he had only three months to live. Recent reports have said he could live as long as seven more years.
His arrival at the Tripoli airport last year was met by huge cheering crowds of relatives and other fellow Libyans, many of them waving Scottish flags.
The decision to free al-Megrahi, the only person convicted in the 1988 explosion aboard a Pan Am flight over Lockerbie, Scotland, that killed 270 people, has been sharply criticized both in the U.K. and the U.S. The flight was on its way from London to New York, and most of the victims were Americans.
Four Democratic senators have renewed their call for an investigation into his release, amid claims it might have been the result of pressure from the BP oil company to secure an oil drilling agreement with Libya, a claim BP and Scottish officials deny.
A British Foreign Office statement sent to AOL News today repeated Prime Minister David Cameron's recent assertion that the release was a mistake, and added: "Particularly on this anniversary, we understand the continuing anguish that Megrahi's release has caused his victims both in the U.K. and the U.S. He was convicted for the worst act of terrorism in British history. Any celebration of Megrahi's release would be tasteless, offensive and deeply insensitive to the victims' families. We have made our concerns clear to the Libyan government."
A similar statement was made to the Libyan government by U.K. Ambassador Richard Northern, who told senior officials that any public events in support of al-Megrahi could damage the recently improved ties between the two countries.
Al-Megrahi's health is "stable," a close relative told Agence France-Presse this week, adding that he leaves home only for hospital visits.
The editor of the Akhbar Libya website, Ashour Sharris, was quoted by The Daily Mail as saying he had been told by "a reliable" but unidentified medical source in Tripoli that al-Megrahi "could live up to seven years."
He added: "They are looking after him very well. He has 24-hour care in his home, and wherever he goes he has doctors with him."
Scotland's Justice Minister Kenny MacAskill, who made the decision to release al-Megrahi, defended his actions Thursday, saying the three-month prognosis was "a reasonable estimate."
However, the Scottish Labor Party leader, Iain Gray, was quoted as saying: "How much compassion did his government show to the American relatives of the 270 people killed at Lockerbie?"
According to The Guardian, Gray added that significant doubt had been cast on the medical evidence. "That evidence should be published, and then I think the Scottish government should admit that they got this decision wrong," he said.
A defense of the decision to release al-Megrahi was also made by the Scottish First Minister Alex Salmond, who said in a BBC radio interview that it was difficult "trying to exactly define the life prognosis of somebody with terminal cancer."
Scotland has freed 27 prisoners on compassionate grounds, the BBC reported, and only two, including al-Megrahi, have lived for more than a year after being released.