Abdelbaset Ali Mohmet al-Megrahi reported to have been hospitalised three days ago.
The convicted Lockerbie bomber, released from a Scottish jail last month on compassionate grounds because of ill health, has been admitted to an intensive care unit in Tripoli, a Libyan official said on Wednesday.Abdelbaset Ali Mohmet al-Megrahi, who has prostate cancer and was given only three months to live when he was released on August 20, was hospitalised "three days ago," said the official, who spoke on condition of anonymity.
"He is in a critical state. He is undergoing chemotherapy sessions," said a person close to Megrahi, adding: "Even his family are forbidden to visit, on doctors' orders."
Megrahi is in the Tripoli Medical Center's cancer ward, a security officer told an AFP correspondent at the scene.
Plain clothes police could be seen preventing visitors from going in and a security barrier blocked access to cars.
The 57 year-old former intelligence officer was the only man convicted of the 1988 bombing of Pan Am Flight 103 above the Scottish town of Lockerbie on December 21, 1988, which killed 270 people.
He received a jail term of at least 27 years in 2001 and served eight years before his release.
Scottish Justice Secretary Kenny MacAskill freed Megrahi on compassionate grounds, saying that the Libyan was dying from his illness.
Megrahi's release - and the hero's welcome he received on his return to Tripoli - drew a furious US reaction, both from President Barack Obama's administration and families of the 189 US victims of the atrocity.
The Scottish government was defeated by 73 votes to 50 on Wednesday in a parliamentary vote over Megrahi's release of the Lockerbie bomber.
Opposition parties joined together to condemn the decision, though the move falls short of a vote of no-confidence in the government.
British Prime Minister Gordon Brown insisted Megrahi's release was entirely a matter for the Scottish government.
"There was no conspiracy, no cover-up, no double-dealing, no deal on oil, no attempt to influence Scottish ministers, no private assurances by me to Colonel Kadhafi," he said.
Brown, who met Kadhafi in July, underlined the strategic aim of bringing Libya back into the international fold, but stopped short of confirming that he had favoured releasing Megrahi from prison before his death.
However, Foreign Secretary David Miliband acknowledged that London did not want the Libyan to die in Greenock prison, west of Glasgow.
"We did not want him to die in prison... we weren't seeking his death in prison," Miliband told BBC radio, while insisting: "There was no pressure from the British government on the Scots."
On Tuesday, documents were released by British and Scottish authorities about the case, which London hoped would counter charges that Megrahi was released as part of a deal to facilitate a huge oil and gas deal with oil-rich Libya.
Miliband said Brown told Kadhafi there was no question of a deal over Megrahi.
"He was absolutely clear in his meeting with Colonel Kadhafi that he could not instruct, and he could not give comfort about the Megrahi (case) .. there was no way for us to control Megrahi's fate," said the foreign minister.