The International Criminal Court prosecutor said on Friday that his office was in "informal contact" with the late Muammar Gaddafi's fugitive son Saif al-Islam over his possible surrender to the war crimes court.

Saif al-Islam went on the run after forces loyal to Libya's new rulers captured and apparently killed his father outside his hometown of Sirte. Saif al-Islam is believed to have fled across Libya's southern border into Niger.

"Through intermediaries, we have informal contact with Saif. The office of the prosecutor has made it clear that if he surrenders to the ICC, he has the right to be heard in court, he is innocent until proven guilty. The judges will decide," prosecutor Luis Moreno-Ocampo said in a statement.

"Additionally, we have learnt through informal channels that there is a group of mercenaries who are offering to move Saif to an African (country) not party to the Rome Statute of the ICC. The Office of the Prosecutor is also exploring the possibility to intercept any plane within the air space of a state party in order to make an arrest," he said.

Countries which are not party to the Rome Statute are not obliged to hand over suspects.

"This is a legal process and if the judges decide that Saif is innocent, or has served his sentence, he can request the judges to send him to a different country as long as that country accepts him," it added.