Meanwhile, Ha'aretz reported that Israeli government has approved the call-up of tens of thousands of IDF reservists.

A statement issued by Israeli Prime Minister's office said that in accordance with a secret cabinet discussion Friday, the government ordered the armed forces "to draft the necessary reservists, on a scale of tens of thousands of troops."

Shortly after IDF soldiers entered Gaza, Israeli Defense Minister Ehud Barak said that the IDF operation in Gaza will be neither short nor easy.

Barak, who made the remarks while addressing the nation in a special televised press conference, told the nation that Israel was not eager to wage war, but could not abandon its citizens, residents of the south, who have been victimized by Hamas rockets.

Smoke trails of an Israeli air force jet is seen above the southern Israeli city of Sderot on January 3, 2009. Israeli artillery shelled Gaza Strip on Saturday, following with the ground offensive. [Yin Bogu/Xinhua]

"The campaign won't be easy and it won't be short," he said, noting that the operation entails the risking of Israeli lives. "I know well the dangers that come with an offensive, and what the heavy price will be."

"I don't want to fool anyone. The residents of southern Israel will also undergo some tough times," the defense minister continued.

He also addressed the possibility of an escalation in violence in northern Israel, along the border with Lebanon, saying that "we hope that the northern front will remain calm, but we are prepared for any possibility."

Hours before the IDF ground incursion, the IDF fired artillery shells into Gaza, which was the first artillery fire since the Cast Lead Operation starting last Saturday.

According to local news service Ynet, IDF artillery cannons began pounding the eastern sector of the Gaza Strip around 4 p.m. (1400 GMT) Saturday.

This is the first time in three years that the IDF has fired artillery shells at Gaza targets, said Ynet, adding that most shells landed in what the Palestinians characterize as the "security zone" close to the Gaza Strip fence.

According to Mo'aweya Hassanein, chief of emergency and ambulance services in the Palestinian health ministry, the Cast Lead operation has so far claimed 462 Palestinians.

Israeli soldiers guard at Gaza border after Israel started the ground operation on January. 3, 2009. The Israel Defense Forces (IDF) Saturday evening began its ground operation in the Hamas-ruled Gaza Strip, an IDF spokesman told Xinhua. [Yin Bogu/Xinhua]

(Xinhua News Agency January 4, 2009)