Israel's military has begun the first stages of a planned ground offensive in Gaza City, causing Palestinians to flee.

It's pressing ahead with its plan to occupy the war-torn city despite international criticism.

New Zealand's one of 27 countries demanding Israel give foreign media access to Gaza to cover the “unfolding humanitarian catastrophe”.

Europe Correspondent Vincent McAviney told Ryan Bridge Israeli hostage families are concerned about the 60-thousand reserve force soldiers to set foot in Gaza.

He says they think hostages will be executed or caught up in the firing, while soldiers try to access the tunnel network where it's believed the rest of Hamas remain.

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