As it happened, talking with Israelis remained enough of a taboo to get Mr. Aman into trouble afresh.
He came in for vituperative criticism online, and early Thursday morning, a freelance Gaza journalist, Hind Khoudary, posted angry denunciations on Facebook of Mr. Aman and others on the call, tagging three Hamas officials, including Mr. Al-Bozom, to ensure it got their attention.
An arrest warrant was issued by the Hamas military prosecution, which handles accused collaborators with Israel, would-be suicide bombers and other serious security threats, Mr. Al-Bozom said. He did not identify or say how many other youth committee members had also been detained.
Separately, the Hamas armed wing and other militant groups issued a joint statement declaring that “normalization in all its forms and activities is treason, a crime, and religiously, nationally and morally unacceptable.”
Only days earlier, the Gaza Youth Committee formally joined the Alliance for Middle East Peace, an international coalition of groups seeking to foster Israeli-Palestinian cooperation. John Lyndon, the alliance’s chief executive, said that international law enshrined the right to “seek, receive and impart information and ideas through any media and regardless of frontiers.” The youth committee’s work — “speaking to people right around the world about the situation in Gaza, and the need for them and the two million people living there to enjoy the freedom, peace and security that is denied to them — falls squarely within that right,” he said.
There was no word late Friday about Mr. Aman’s condition. Mr. Aman’s father, reached by telephone, said he and his wife had been told to bring clean clothes for their son to the Internal Security headquarters in Gaza City. They did as instructed, he said, but were sent away without being able to see him.
David M. Halbfinger reported from Jerusalem and Iyad Abuheweila from Gaza City.