The son of former dictator Colonel Muammar Gaddafi was sentenced to death earlier this week - but he is already being held by rebels elsewhere.

Saif al Islam Gaddafi was convicted during a mass trial in Tripoli of murder and inciting genocide during the country's 2011 uprising.

He is being held in the southern town of Zintan by a rebel group that opposes the government in Tripoli and refuses to hand him over.

"He has been something of a war trophy for them...Saif al Islam is too useful to them alive, so they will not give him up without a fight" , foreign affairs columnist with the Irish Independent - Mary Fitzgerald - told the Pat Kenny Show.

Saif Gaddafi is also wanted by the International Criminal Court on charges of crimes against humanity.

Educated at the London School of Economics, he was the most high-profile of Colonel Gaddafi's eight children.

He was once considered de-facto prime minister and tipped by Western governments to one day lead the country towards democracy.

But he refused to abandon his father when protests erupted in several Libyan cities in early 2011.

"There was a considerable amount of support for the death sentence handed down to him this week", Fitzgerald said.

But she also warned that: "Tripoli itself, where the court sits, is controlled by militia men - everything in Libya right now is controlled by militia men".

"Libya doesn't have politics as such, it has militia politics".

On Saif Gaddafi himself, Fitzgerald said: "He claimed to be concerned about past abuses of his father's regime - particularly in relation to human rights".

"But all of that was basically thrown up in the air in the first weeks of the uprising against his father in February 2011, when Saif al Islam gave a televised address - which was really quite extraordinary".