Abdelbaset al-Megrahi, 59, was found at his mother's posh villa in the Libyan capital, The Sun reported.
Cancer-affected al-Megrahi was in coma and on an intravenous drip.Al-Megrahi was convicted in the bombing of the Pan Am Flight 103 over Scotland in 1988.
He was released from a Scottish jail on compassionate grounds in 2009, and returned to a hero's welcome in Libya.
Al-Megrahi was found after neighbours in Tripoli directed CNN to a luxury home fitted with security cameras and floodlights.
Relatives said they rescued him from hospital a few days ago and took him home. They said he was close to death and claimed they got no help from the Gaddafi regime.
"He's stopped eating and some times he is in a coma. We just give him oxygen. Nobody gives us any advice. There is no doctor. We don't have any phone line to call anybody," his son Khaled was quoted as saying.
Libyan rebels are now refusing to extradite al-Megrahi to Britain to serve out the rest of his life sentence for the plane bombing.
Rebel justice minister Mohammed al-Alagi said: "Libya has never extradited or handed over its citizens to a foreign country. We shall continue with this principle."
