As the offensive entered its eighth day Palestinian medical sources said 464 Palestinians had died and more than 2,000 have been injured.
The news comes as the United Nations Security Council is to meet on Saturday evening to discuss the crisis.
|The Israeli defence minister said Israel
had weighed all options before the raids [AFP]
It also comes after the latest air raids in Gaza on Saturday when an Israeli strike on a northern Gaza town killed at least 11 people, including one child, who were praying in a mosque.
Four Israelis have also been killed in rocket fire into southern Israel.
There has been no official confirmation from either side of casualties from Saturday's ground invasion so far, although Zeina Awad, Al Jazeera's correspondent in Jerusalem, said Israeli media was reporting that several Hamas fighters had been killed at the start of the ground offensive.
The Reuters news agency also said a senior Hamas official had said that its fighters had killed a number of Israeli soldiers, but neither report could be confirmed.
Ehud Barak, the Israeli defence minister, said on Saturday that the operation was aimed at forcing Hamas "to stop its hostile activities against Israel and bring about significant change".
"We have carefully weighed all our options, we are not war hungry but we should not allow a situation where our towns are constantly targeted by Hamas," he said.
Mark Regev, an Israeli government spokesman, later told Al Jazeera on Saturday that the "single aim" of the offensive was to halt Hamas rocket attacks into Israeli territory.
"Ultimately Hamas is solely responsible for this crisis and today they are paying a price for that," he said.
Hamas has vowed to defeat the Israeli army following the invasion, with Osama Hamdan, a senior official for Hamas in Beirut, Lebanon, telling Al Jazeera that "military operations will not win for the Israelis".
On Friday, Khaled Meshaal, the political leader of Hamas, warned that any Israeli ground offensive would lead to a "black destiny".
Al Jazeera's Ayman Mohyeldin said that power lines have been cut throughout the strip and more than 250,000 people in northern Gaza are without electricity.
"The biggest concern is a ground invasion could result in urban warfare," he said.
"Rockets are being fired from deeper and deeper within Gaza and if Israel's intention is to prevent such attacks how far into Gaza, an area densely populated with civilians, will they need to go?"
Speaking to Al Jazeera, James Denselow, a Middle East specialist from Kings College, London, said: "Hamas operates as an asymmetrical force. It knows its strength and knows indiscriminate rockets can cause alarm.
"This is why the Israeli army has used air strikes to 'soften' the ground followed by an assault at night when low-tech armies such as Hamas find it very hard to fight."
Israeli artillery had started firing shells into the Gaza Strip for the first time on Saturday, ahead of the ground offensive.
Ofir Gendelman, an Israeli foreign ministry spokesman, said: "All we [are] asking for is to create a normal life for people of Israel. We'll keep on targeting Hamas objectives until the situation on the ground there is transformed.
"They [Israeli ground forces] will be completing the mission of the air force, going for Hamas headquarters and weapons caches and giving a blow to their capability to launch attacks into Israel.
"It will take quite a number of days to get the job done."
Marwan Bishara, Al Jazeera's senior political analyst, said: "Israel can claim in various stages that it has won this or that war against Arabs, but it is obvious since the invasion of Lebanon in 1982 that there is no military solution to Israel's security.
"It cannot bomb its way into peaceful co-existence. Israel is trying to do all it can to destroy Hamas but with more than 400 dead, there will be more than 400 more new recruits in Gaza.
"It has taken this path and will probably pay the price in the long term, short term it's the Palestinians who pay the price."