Three Palestinian militant groups that captured an Israeli soldier demanded in a statement this morning that Israel free 1,000 Arab prisoners held in its jails and end its offensive.
The document titled "Military Statement Number Two", which was faxed to news agencies, did not specify whether the demands were for the release of Corporal Gilad Shalit.
But a spokesman for the military wing of the governing Hamas group, one of the three factions, said they were conditions for freeing Shalit.
It was the second statement released by the groups since Shalit was abducted in a cross-border raid on Sunday.
"We are declaring to the public our just and humanitarian demands," it said. It repeated an earlier demand for the release of women prisoners and minors in exchange for information on Shalit, but made the added request for Israel to free 1,000 "Palestinian, Arab and Muslim prisoners."
It said these would have to include all Palestinian faction leaders as well as humanitarian cases. The statement cast doubt on hopes voiced by mediators that Shalit could be freed soon.
"In spite of the good efforts of the mediators who tried in silence to speed up the treatment of this humanitarian matter, the enemy and their political leadership are still under the pressure of the security and military command," it said.
"The escalation and arrogance mean the enemy will be responsible for the bad consequences," it said. There was no specific threat to Shalit.
As well as Hamas's armed wing, the Popular Resistance Committees and Army of Islam carried out the attack in which he was captured. They have not said their statements are an admission that they are holding him.
Israeli tanks entered the southern Gaza Strip this week in the biggest push into the territory since Israel pulled out troops and settlers last year after 38 years of occupation. The offensive, which has included air strikes and artillery, is intended to force Shalit's release.