The Lockerbie bomber has reportedly been admitted to hospital for a blood transfusion.
Abdelbaset al-Megrahi's health is said to have "deteriorated quickly".
He is the only man ever convicted of bombing the Pan Am Flight in 1998, killing 270 people.
He was sentenced to life in prison in 2001, but was released on compassionate grounds in August 2009, after being diagnosed with terminal cancer.