Asked by reporters at a base in southern Israel about targeting Hamas officials, Amir Peretz said: "We will definitely act against any organisation or element that is planning operations.
"No one has an insurance policy. No one endangering Israelis can turn his name or title into an insurance policy."
Hamas, which now heads the Palestinian government, renewed cross-border rocket and mortar attacks on Saturday after seven people were killed on a Gaza beach on Friday in an attack blamed on Israel.
Speaking at an army base near the Gaza Strip, Peretz said he sent a condolence message to Mahmoud Abbas, the Palestinian president, expressing deep regret at the bloodshed on the beach but said a military probe into the cause of the explosion would be completed only in a day or two.
In the Gaza Strip, thousands of Palestinian mourners wept with 7-year-old Huda Ghalya as she kneeled to kiss her dead father before he, her mother and three siblings were buried.
The 4-month-old, 3-year-old and 10-year-old siblings and their parents were among the seven killed during a seaside outing on Friday after Israeli artillery shelled the area to curb cross-border rocket fire.
At least 20 people were also wounded.
Huda had been swimming in the Mediterranean when the blast tore up the beach.