The hunt for a jailed gun killer who absconded while on unescorted leave from prison has entered its fourth day.

John McDermott Wilson, 50, failed to return to the Greenock prison after unescorted leave on Friday. The public have been warned not to approach him.

He was last seen outside Central Station in Glasgow around 4.05pm on Friday. Wilson was convicted of murder in 1991 and is serving a life sentence.

Wilson was jailed for life in 1991 for shooting Stephen Barnes dead as he stood at a bus stop. He mocked the family at court after his conviction, shouting "bang, bang" as they sat in the gallery.

He was also convicted of the attempted murder of Mr Barnes' friend, Andrew Ralston, who was with him at the bus stop.

Wilson is described as around 5ft 5in tall, of medium build with fair complexion, brown thinning hair, blue eyes and is clean shaven. He also has a small scar on his lower lip.

When last seen, he was wearing a blue jacket, a grey sweatshirt, a blue T-shirt, navy jeans, black boots and a black beanie hat.

A statement from Police Scotland said: "Officers have been carrying out extensive enquiries to trace Mr Wilson, but attempts to locate him have so far proved unsuccessful. If you see John Wilson, do not approach him but contact police.

"Anyone who has seen John Wilson or who has information or knowledge as to his whereabouts is asked to call officers at Greenock Police Office on the non-emergency number 101."