Saif al-Islam, the son of the late Libyan leader Muammer Gaddafi, believes he should be tried before the International Criminal Court (ICC) if justice is to be served, his defence lawyers have said.

"The only way for Libya and the Libyan people to have justice is for the ICC to try this case in a fair, impartial and independent manner," he was quoted as saying in a defence document submitted to the court on Tuesday.

The Hague-based ICC has issued warrants against both Seif and his late father's intelligence chief, Abdullah Senussi, for crimes against humanity committed while trying to put down last year's bloody revolt.

Saif has been in custody in the southern Libyan town of Zintan since his November capture in the wake of the uprising that toppled Gaddafi after more than 40 years in power.

The ICC and the Libyan government are locked in a dispute over where Saif should be tried.

"I would have liked to have been tried in Libya by Libyan judges under Libyan law in front of the Libyan people," Saif was quoted as saying in the document, issued after ICC lawyers visited him last month.

"There will also be no truth if witnesses are faced with possible life sentences for simply testifying in my favour.

"I am not afraid to die but if you execute me after such a trial you should just call it murder."

Saif's lawyer Melinda Taylor and three other ICC staff members were freed earlier this month after being held in Libya for almost four weeks while visiting Gaddafi's son on behalf of the court.

Taylor said after her release that she believed it would be "impossible" for Saif to be tried in an independent and impartial manner in Libyan courts.