Israel will use "enormous force" against the Hamas militant group, Prime Minister Benjamin Netanyahu has warned.
He says the Israel Defense Forces' retaliation for the worst attack on Israeli soil in decades has only just begun.
More than 700 people have been killed in Israel since Saturday's surprise attack, including 260 people massacred by Hamas gunmen at a music festival.
Since Israel began striking Gaza in response, nearly 600 people have died.
Speaking to local mayors on Israel's southern border earlier, Netanyahu said the country's response would "change the Middle East".
A statement, released by Netanyahu's office about the visit did not elaborate on this, but it did say he had told the council heads that what Hamas will experience will be "difficult and terrible".
He told visiting officials from southern Israel, according to the AFP news agency, that "what Hamas will experience will be difficult and terrible".
Netanyahu went on to say that "this is only the beginning... we are all with you and we will defeat them with force, enormous force".
Israel's defence minister earlier ordered a "complete siege" of the Gaza Strip, cutting off food, fuel, electricity and water supplies.
Nine US citizens are now confirmed dead in Israel, while more than 10 British citizens are feared dead, or missing.
Dozens of people remain kidnapped by Hamas and their families are desperately searching for information.
