AMSTERDAM (AP) — The International Criminal Court on Saturday demanded the release of four staff members it said were being detained in Libya, where they were meeting with the imprisoned son of the deposed dictator Col. Muammar el-Qaddafi.

“We are very concerned about the safety of our staff in the absence of any contact with them,” the court president, Sang-hyun Song, said in a statement in The Hague. “These four international civil servants have immunity when on an official I.C.C. mission.”

The four include at least one lawyer the court has assigned to help defend the legal interests of the Qaddafi son, Seif al-Islam el-Qaddafi, who was detained by fighters in November.

Mr. Qaddafi is at the center of wrangling between the international court and the new government in Tripoli, both of which have drawn up plans to prosecute him on war crimes charges. He has also been caught in a power struggle between the national authorities in Tripoli and the local ones in Zintan, Libya, who arrested him and have ignored requests from the capital to hand him over.