Ismail Zitouny / Reuters, file

Seif al-Islam Gadhafi, the son of onetime Libyan leader Moammar Gadhafi, is pictured sitting in a plane in Zintan after his capture in November.

TRIPOLI -- Representatives of the International Criminal Court arrived in Tripoli on Sunday to try to secure the release of a detained delegation visiting Moammar Gadhafi's captured son, a Libyan official said. 

The four-member delegation was being held by a militia group in the western mountain town of Zintan after one of its lawyers, Australian Melinda Taylor, was found carrying documents regarded as suspicious for Seif al-Islam Gadhafi, a Libyan lawyer and a militia member told Reuters on Saturday.

The president of the international war-crimes court demanded their immediate release. 

ICC via EPA

The ICC delegation was being held in the western mountain town of Zintan after one of its lawyers, Australian Melinda Taylor, was found carrying documents regarded as suspicious.

"An (ICC) delegation arrived [Sunday] in Tripoli. They are holding meetings with officials about this," said the Libyan official, without giving further details. 

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Seif al-Islam is at the center of a wrangle between the international court and the new government in Tripoli, both of which have drawn up plans to prosecute him for alleged war crimes. 

Under international law, a country has the first right to try suspects for crimes committed on its own soil. But the ICC indicted Seif al-Islam before the fall of his father's regime and cannot drop his case until it is convinced that Libya's new government will prosecute him for the same crimes -- and that it is capable of giving him a fair trial. 

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Reflecting Libya's wider problem of powerful local militias and a weak central government, the Zintan brigade holding Seif al-Islam said it would not heed the government's request to release the four ICC staff before questioning them. 

"They are still under investigation," a member of the brigade said. "The visiting delegation won't see them just yet." 

The ICC has previously expressed concern at the conditions under which he is being held. Human rights groups also question whether Libya's justice system can meet the standards of international law. 

A Libyan lawyer said the suspicious documents included letters from Seif al-Islam's former right-hand man Mohammed Ismail, as well as blank documents signed by the prisoner. 

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The international court said the 36-year old Taylor has been working at the ICC since 2006 as counsel in the office that represents ICC indictees' interests before the appointment of a formal defense counsel. 

The ICC named the three other staff members as Helene Assaf, an ICC translator and interpreter since 2005; Esteban Peralta Losilla, the chief of the Counsel Support Section at the ICC; and Alexander Khodakov, a Russian career diplomat who is the external relations and cooperation senior adviser at the registry of the ICC. 

Reuters and The Associated Press contributed to this report. 

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