Australian Foreign Minister Bob Carr Monday headed to Libya to press for the release of an International Criminal Court team who are being held after meeting the son of dead dictator Moamer Kadhafi.
The delegation, including Australian Melinda Taylor and colleagues from Lebanon, Russia and Spain, were detained on June 7 as they helped Seif al-Islam choose a defence lawyer.
Libyan officials have alleged Taylor was carrying a pen camera and attempting to give Seif a coded letter from his former right-hand man, Mohammed Ismail, who is on the run.
The Hague-based ICC wants to try Seif, 39, for crimes against humanity.
Carr, who was in the region after attending a meeting of the Non-Proliferation and Disarmament Initiative in Istanbul, said he would be pushing for their release.
"I am cautious about commenting on the specifics of the allegations, and have modest expectations from the talks today," he said ahead of scheduled meetings with Libyan authorities.
"But we will press the case that Ms Taylor is in Libya under the mandate of the ICC and United Nations Security Council, and this mandate provides a legal immunity."
On Friday, the UN Security Council expressed "serious concern" over Libya's detention of the four.
It reminded Libyan authorities that they have to cooperate with the ICC under UN resolutions on the conflict last year that led to the overthrow of late strongman Kadhafi.