Al-Megrahi is the only man convicted in the 1988 bombing of the Pan Am flight over Scotland that killed 270 people. In August he was freed from a Scottish prison on compassionate leave and returned to Libya.
A source close to the family of the Lockerbie bomber Abdul Baset al Megrahi told Sky News Thursday his death is imminent and every day is "expected to be his last."
Suffering from prostate cancer, the Libyan's health has rapidly deteriorated -- and his relatives said he has been in a coma and on life support for around a week.
Al Megrahi -- who was convicted of killing 270 people by bombing a Pan Am jet in 1988 -- has been unable to walk for a number of weeks and is not expected to recover.
A source close to his family told Sky News: "He is on life support and has been for some days. Many people have been waiting for him to die.
"That day is coming very soon. Every day, his loved ones expect it to be his last."
Al Megrahi has survived far beyond the three months expected after his release on compassionate grounds from Britain's Greenock Prison by the Scottish government in August 2009.
The decision provoked international outrage and was roundly condemned by victims' relatives and senior U.S. lawmakers, including President Barack Obama -- and anger has grown the longer al Megrahi has lived.
Since his release, he has been receiving chemotherapy in Libya. Medical observers have suggested that being amongst his family may also have helped prolong his life.
Al Megrahi has always protested that he is innocent of the Dec. 1988 bombing that brought down a plane flying from London's Heathrow Airport to New York.
British relatives have been vociferous amongst a group of campaigners who believe the Libyan was wrongly convicted and have long demanded an inquiry into the investigation and court proceedings that convicted him.