Saif al-Islam Gaddafi feared he would be 'murdered' by Libyan authorities under the guise of a court trial, according to a new filing lodged by the defence lawyers of Muammar Gaddafi's son before the International Criminal Court (ICC) on Tuesday.

"I am not afraid to die but if you execute me after such a trial you should just call it murder and be done with it," the younger Gaddafi was quoted by Reuters as saying in a document prepared by his lawyers led by Aussie lawyer Melinda Taylor.

The ICC filing confirmed Ms Taylor's allegations earlier this July that Saif al-Islam has been "irrevocably prejudiced by the new Libyan government," and his chances of getting a fair trial in Libya appears remote at the moment.

Saif al-Islam has been detained by Zintan authorities since November 2011 and the ICC wants to try him before The Hague for crime against humanity committed during the Libyan revolution that toppled the Gaddafi regime.

But the court has been at odds with Tripoli on where to try Mr Gaddafi's son, with Libyan authorities insisting that the judicial procedure must be conducted in Libya and within the rules by Libyan judicial system.

The conflict between Libya and the ICC further heightened when Ms Taylor and her ICC team were detained for more than three weeks in Zintan following their meet with Saif al-Islam.

Libya has accused Ms Taylor of passing secret messages to her client, which she vehemently denied.

Following her release from custody, the Aussie lawyer accused Libya of misleading her ICC team be secretly monitoring their privilege audience with Saif al-Islam.

"They also seized documents which were covered by legal professional privilege and ICC protective orders," Ms Taylor was reported by The Daily Telegraph as saying in a statement she issued shortly after her release from detention.

Reuters reported the new ICC filing this week, which claimed that a certain Ahmed Amer, a Zintan official, "was planted in the room to deliberately trick the delegation."

"(Mr Amer) came back into the room and (in the presence of the ICC interpreter), started shouting that this statement was very dangerous, violated Libyan national security, and that the Defence could not have it back," the ICC filing further said, which largely confirmed Ms Taylor's account.

Ms Taylor warned too the prospect of a fair trial for the Gaddafi son is dim, stressing that "irrespective of any issues concerning my own personal conduct, the rights of my client, Mr Saif al-Islam, were irrevocably prejudiced during my visit to Zintan."

"It is the position of the defence that these recent events have completely underscored that it will be impossible for Mr Gaddafi to be tried in an independent and impartial manner in Libyan courts," she added.

Saif al-Islam affirmed such claim as he reportedly told the ICC team led by Ms Taylor that "I would have liked to have been tried in Libya by Libyan judges under Libyan law in front of the Libyan people."

But such scenario is next to impossible if witnesses that would give out testimonies in favour of the younger Gaddafi face threats of harm and retribution, Saif al-Islam reportedly told the ICC team during their meet.

"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," Agence France Presse (AFP) quoted Saif al-Islam as saying in the ICC filing.