Three Palestinian groups purporting to hold Shalit demanded the release of women and children under 18 held in Israeli prisons, the first demand issued since the serviceman was captured 36 hours earlier.
The statement was signed by Hamas' military wing, the Saladdin Brigade, and the Army of Islam. The last two groups are offshoots of the small Popular Resistance Committees, which has strong links to Hamas.
"The occupation will not get any information about its missing soldier until it commits to the following: First, the immediate release of all women in prison. Second, the immediate release of all children in prison younger than 18," the fax read.
Abu Mujahid, a spokesman for the PRC, confirmed the statement was authentic.
Shalit, a 19-year-old Cpl., was captured Sunday morning in an attack by Hamas-linked operatives on an IDF post near the Gaza Strip border.
Feverish diplomatic efforts have been underway to secure his release, and the groups themselves noted they were issuing the demands "in response to various mediation efforts and other intervention."