The 59-year-old former hunger strike leader was believed to be in a coma, with relatives keeping a bedside vigil at Belfast City Hospital, where his condition was described as "critical".

Hughes, nicknamed The Dark, was the Belfast commander of the IRA and a leading figure in the terror organisation during the Troubles.

He led hunger strikers for several weeks in 1980, just months before the second jail fast in which Bobby Sands and nine other republican prisoners starved themselves to death.

In recent years he was an outspoken critic of Sinn Fein.

When he was released from the Maze in 1986, Hughes kept a low public profile, but on a number of occasions has attacked the Sinn Fein leadership, claiming that the move towards armalite to ballot box had "created a class of professional liars".

Hughes had been arrested in 1974 - after escaping from jail a year earlier - and jailed for 15 years on guns and explosives charges. He was later handed another five-year sentence for assaulting a prison warder.

Last year he revealed details of an IRA meeting he attended in Donegal with Martin McGuinness in 1986 in which the now deputy First Minister authorised a "major push" in the IRA's campaign of violence.

The revelation contradicted Mr McGuinness' evidence under oath to the Bloody Sunday inquiry claiming he had left the IRA in the 1970s.

cmcguigan@belfasttelegraph.co.uk