New Delhi, July 22 -- Israeli troops for the first time Monday pushed into areas of a central Gaza city where several aid groups are based, in what appeared to be the latest effort to carve up the Palestinian territory with military corridors.

Deir al-Balah is the only Gaza city that has not seen major ground operations or suffered widespread devastation in 21 months of war, leading to speculation that the Hamas militant group holds large numbers of hostages there. The main group representing hostages' families said it was "shocked and alarmed" by the incursion and demanded answers from Israeli leaders.

Israel says the seizure of territory in Gaza is aimed at pressuring Hamas to release hostages, but it is a major point of contention in...