Israel today warned the people of Gaza that its attacks which have so far killed more than 300 were a "war to the bitter end".
The statement from defence minister Ehud Barak came as jets obliterated symbols of Hamas power on the third day of its overwhelming assault.
They hit a house next to the Hamas premier's home, devastated a security compound and flattened a five-storey building at a university closely linked to the Islamic group.
Meanwhile there were reports that the Israeli navy had begun bombarding the area from the sea.
The death toll rose to 315, including seven children under the age of 15.
Israel says the onslaught is aimed at ending the barrage of rockets being fired at its towns by Hamas. So far it has been only partly successful with sirens warning of incoming rockets sending Israelis scrambling for cover throughout the day.
One medium-range rocket fired at Ashkelon killed an Arab building worker and wounded several others. He was the second Israeli killed since the beginning of the offensive, and the first person ever to be killed by a rocket in Ashkelon, a city of 120,000.
Most of those killed since the attacks began on Saturday were members of Hamas security forces, although the precise numbers remain unclear.
Israel's intense bombings - more than 300 airstrikes since midday Saturday - reduced dozens of buildings to rubble. The military said naval vessels also bombarded targets from the sea.
One strike destroyed a five-storey building in the women's wing at Islamic University, one of the most prominent Hamas symbols in Gaza.
Others hit a compound controlled by Preventive Security, one of the group's chief security arms, and destroyed a house next to the residence of Ismail Haniyeh, the Hamas prime minister. Like other Hamas leaders, he is in hiding.
Defence minister Mr Barak told Israel's parliament in a special session that Israel was not fighting the residents of Gaza.
"But we have a war to the bitter end against Hamas and its branches," he said.
He also said the goal was to deal Hamas a severe blow and that the operation would be "widened and deepened as needed".
Israel began Saturday's assault by targeting Hamas security installations, and has broadened the attacks since then. Yesterday planes struck dozens of smuggling tunnels under the Gaza-Egypt border, cutting off a key lifeline that had supplied Hamas with weapons and Gaza with commercial goods.
Gaza's nine hospitals were overwhelmed.
In Israel, 17 people have been killed in attacks from Gaza since the beginning of the year, including nine civilians - six of them killed by rockets - and eight soldiers.
Israeli security officials have warned that the militants' range now includes Beersheba, a major city 30 miles from Gaza.
In Jerusalem, Israel's Cabinet approved a call-up of 6,500 reserve soldiers in apparent preparation for a ground offensive.
The final decision to call up reserves has yet to be made by Mr Barak, and the Cabinet decision could be a pressure tactic. Military experts said Israel would need at least 10,000 soldiers for a full-scale invasion.
Israel has doubled the number of troops around Gaza and also deployed an artillery battery. Several hundred reservists have already been summoned to join their units, but no full combat formations have been mobilised so far.
The assault has sparked diplomatic fallout. Syria decided to suspend its indirect peace talks with Israel, and the UN Security Council called on both sides to halt the fighting and asked Israel to allow humanitarian supplies into Gaza.
The prime minister of Turkey, one of the few Muslim countries to have relations with Israel, called the air assault a "crime against humanity", and French President Nicolas Sarkozy condemned "the provocations that led to this situation as well as the disproportionate use of force".
The Palestinian president, Mahmoud Abbas, who heads a moderate government in the West Bank and is holding peace talks with Israel, issued his strongest condemnation yet of the operation, calling it a "sweeping Israeli aggression against Gaza" and saying he would consult with his bitter rivals in Hamas in an effort to end it.
The carnage inflamed Arab and Muslim public opinion, setting off street protests in Arab communities in Israel and the West Bank, across the Arab world, and in some European cities.
Demonstrations are due to continue today at 5pm outside the Israeli Embassy in Ballsbridge, Dublin by the Irish Anti-war Movement.