MacAskill said he decided to free al-Megrahi on compassionate grounds, strictly following the law. 'This decision is mine and mine alone,' said the minister, underlining that the devolved government of Scotland has sole responsibility for judicial matters.

MacAskill, addressing the concerns expressed by the US, and by relatives, said he was aware that there were 'deeply-held feelings' and that 'many will not agree with my decision'.

In a statement issued on his behalf, al-Meghrahi said he was relieved to return to his homeland.

'To those victims' relatives who can bear to hear me say this: they continue to have my sincere sympathy for the unimaginable loss that they have suffered. To those who bear me ill-will, I do not return that to you,' he said.

For him, his 'horrible ordeal' would not end with his return to Libya. 'It may never end for me until I die. Perhaps the only liberation for me will be death.'

'The remaining days of my life are being lived under the shadow of the wrongness of my conviction.'

Al-Megrahi had three months to live, medical evidence showed, according to MacAskill. 'He may die sooner, he may live longer, I can only base my decision on the medical advice before me,' he said.

The decision drew outraged responses from families of the US victims.

'When you say compassionate I feel ill,' said Susan Cohen, whose daughter was killed.

The leader of Britain's opposition Conservative Party, David Cameron, also criticised the release.

'This man was convicted of murdering 270 people, he showed no compassion to them, they weren't allowed to go home and die with their relatives in their own bed and I think this is a very bad decision.'

Saad Jabbar, a lawyer advising the Libyan government, called al-Megrahi's release a 'victory for common sense'.

Insisting that the former convict was not guilty of the attack, the release also served to 'rectify a gross miscarriage of justice', he said.

Al-Megrahi's return to Libya would 'open the way for normalisation' between Britain and Libya and enhance Britain's standing in the Arab world.

'Rest assured that the Scottish government has done the UK a great favour,' Jabbar said. Respect for Britain 'in the eyes of the Arab world will grow'.

The Cairo-based Arab League welcomed Megrahi's release, the Egyptian MENA news agency reported.

'The Arab League welcomes the Scottish court decision to release Megrahi, taking into consideration his serious health condition,' Assistant Secretary General Ahmed Bin Hilli said.