Libyan officials say a team of representatives of the International Criminal Court arrived in Tripoli Sunday to secure the release of four of its staffers detained while visiting Saif al-Islam Gadhafi, the imprisoned son of deposed dictator Moammar Gadhafi.

They say the four-member delegation, including Australian lawyer Melinda Taylor, was detained last Thursday and is being held in Zintan, a town southwest of Tripoli, where Saif al-Islam has been held by revolutionary fighters since his capture in November. The delegation was on an official mission and has been assigned by the court to discuss his defense arrangements.

A militia commander said the four are still under investigation after Taylor was reported to be trying to pass documents to Saif al-Islam during the visit. He said police also found a camera and a recording device “like those used for spying” on another female member of the delegation during a search after the visit.

Court President Sang-Hyun Song requested their immediate release and urged Tripoli to ensure their safety. His statement issued Saturday said “these four international civil servants have immunity when on an official ICC mission.”

Australian Foreign Minister Bob Carr also called for the ICC staffers' release and said Australia wants Libyan authorities to grant immediate consular access to the detainees.

Saif al-Islam is at the center of a wrangle between the ICC and the new government in Tripoli. He is wanted by the ICC for alleged war crimes, but Tripoli wants to try him in his home country.