The families of Israeli hostages held by Hamas in the Gaza Strip have been racked with worry for their loved ones since the military stepped up ground assaults inside the Palestinian territory, a group lobbying for the families said on Saturday.

"This night was the most terrible of all nights ... against the backdrop of the major IDF (Israel Defense Forces) operation in the Strip," the Hostages and Missing Families Forum said in a statement.

It said that the hostages being held by Hamas were being subjected to the same heavy bombardment as Palestinian residents and that their families were racked with "anxiety, frustration" that Israel's long-awaited ground invasion will put them in more danger.