Megrahi lost an appeal against his sentence for mass murder

Abdelbaset ali Mohmed al-Megrahi has begun a challenge against the 27-year punishment period of his jail term.

Lawyers for the Libyan, who was found guilty of killing 270 people in the 1988 bombing, will appear for an initial hearing in court on Friday.

The Crown Office has launched an appeal against the punishment period, arguing that it is "unduly lenient".

The Crown's appeal is due to be heard on 28 June.

The Crown Office said Megrahi was fighting the punishment period on the grounds that it breached his human rights.

Under human rights the sentencing judge must specify a punishment period, after which parole can be considered.

The Crown has already appealed against the punishment part of 27 years and is arguing that the period of 27 years is unduly lenient Crown Office

In a statement, the Crown Office said: "The High Court of Justiciary, the Supreme Criminal Court in Scotland, has granted permission for Abdelbaset Ali Mohmed Al Megrahi, the convicted Lockerbie bomber, to lodge a late appeal against the punishment part of his life sentence.

"The Crown has already appealed against the punishment part of 27 years and is arguing that the period of 27 years is unduly lenient."

"Megrahi has also lodged an associated application seeking to challenge any decision which could extend or delay his release on the grounds that this would breach his rights under the European Convention of Human Rights and Fundamental Freedoms."

Megrahi is serving a life sentence for the bombing of a US airliner which exploded over the Scottish town of Lockerbie in December 1988.

He was convicted of the murder of 270 people after a trial at the High Court sitting at Camp Zeist in the Netherlands in 2001.

Megrahi later appealed against his sentence but lost and was transferred from a special prison in the Netherlands to Barlinnie jail in Glasgow.