The health of the Lockerbie bomber is reported to have deteriorated suddenly.
Abdel Basset al-Megrahi, who was released from prison in Scotland last month on compassionate grounds so he could return home to Libya, is being treated in a special ward at a medical centre in Tripoli.
He has terminal prostate cancer. Doctors say they are waiting for test results from a laboratory in Germany before making a statement.
al-Megrahi's brother says the situation is worrying because he has a high temperature and is unable to speak.
al-Megrahi was sentenced to life in prison in 2001 for his part in blowing up Pan Am flight 103 over Lockerbie, Scotland on 21 December, 1988, killing 270 people.
He received a rapturous welcome when he arrived home in Libya last month.
Defence ties defended by UK govt
The British government says any defence cooperation with Libya is nothing to do with the release of al-Megrahi.
A report in the Daily Telegraph in Britain on Saturday said SAS forces have been training Libyan troops for the past six months.
But government officials have denied any link to the compassionate release of al-Megrahi.
Britain has had unspecified defence cooperation with Libya since Libya renounced weapons of mass destruction in 2003.
Libya supplied the IRA with explosives and weapons during the 1980s, when the SAS was engaged in a campaign against the republican group.
