Keith Siegel and Omri Miran are shown in undated footage released by the armed wing of Hamas.
Moran Yanai was threatened with death and moved from place to place during her ordeal.
The US says no American forces will go ashore but an unnamed "third party" will drive aid into Gaza.
More than 12,000 people rally to urge the prime minister to stay in office as he decides whether to resign.
Political and military leaders are still absorbing the extraordinary exchange of fire, writes James Landale.
Six arrests in quick succession show Germany is being targeted by spies but also that it is fighting back.
