Israeli tanks began pulling out of the southern Gaza Strip early Friday after a day of airstrikes that killed eight Palestinians, the latest stage in Israel's monthlong offensive against Palestinian militants.

Before the pullout, dozens of Israeli tanks pushed into the Gaza Strip and aircraft fired missiles in heavy fighting that mirrored the Israeli offensive against Hezbollah guerrillas in Lebanon.

Palestinian officials said an 8-year-old boy was among those killed in the offensive.

After midnight, Israeli tanks began pulling out of the territory, the military said, after the deepest incursion in southern Gaza during the offensive, with Israeli forces cutting off one of the entrances to the town of Rafah on the Egyptian border for a day.

The United Nations said Thursday it was concerned that "with international attention focusing on Lebanon, the tragedy in Gaza is being forgotten." It called on both Israel and the Palestinian militants to recognize their obligations to protect civilians during hostilities, but singled out Israel for criticism.

"The shelling of sites with alleged military significance that result invariably in the killing of civilians, among them an increasing number of children, cannot be justified," the U.N. said in a statement. "The disproportionate shelling by the IDF (Israeli Defense Forces) must stop."

The U.N. said Israel fired an average of 200-250 artillery shells per day into Gaza, and has killed 175 Palestinians since fighting began more than a month ago. The statement also called on Palestinian militants, who fire an average of 8-9 rockets into Israel each day, to stop.

Fighting on two fronts Thursday, against Islamic militants in Gaza and against Hezbollah guerrillas in southern Lebanon, Israel had one of its heaviest days of fighting since Hamas-linked militants captured a soldier from an Israeli army post near the Gaza frontier more than a month ago.

About 50 tanks, accompanied by bulldozers, pushed into an area close to the Gaza-Egypt border before dawn, taking up positions near the long-closed Gaza airport, residents and Palestinian security officials said.

The forces advanced about five miles, the farthest into south Gaza they have gone since the offensive started in late June, blocking a main highway and the eastern entrance to Rafah, on the Egyptian border.

As the tanks took up positions, Israeli aircraft fired missiles at groups of gunmen, killing four. The strikes wounded 26 Palestinians, at least 10 of them militants, security and hospital officials said.

Forces later fired a tank shell at residents gathering in the area after daybreak, killing an 8-year-old boy and wounding three people, including a 4-year-old girl, hospital and security officials said. The bodies of three more dead people were brought to the hospital early Thursday, but they were not believed to be militants, medics said.

Seventy-five families, comprising 475 people, fled the combat area to a school run by the United Nations Works and Relief Agency— the third time in a month the school had been opened to refugees from the fighting, said Khaled Ashour, UNWRA's area operations assistant.

In addition to the deadly fighting, the U.N. said Israel was creating a situation where Gaza's 1.4 million people faced "a sharp decline in the humanitarian situation."

It criticized Israel for bombing Gaza's only power plant, closing border crossings, blocking access to ports and destroying orchards, bringing much of the coastal strip's economic activity to a halt and "harming the functioning of the entire health system."

Israel launched its Gaza offensive after a June 25 cross-border raid by Hamas-linked militants who tunneled into Israel and attacked an army post, killing two soldiers and capturing a third. Israel has demanded the release of the soldier and an end to the firing of homemade rockets at Israel by Gaza militants.

Israeli ground forces have moved in and out of several parts of the territory regularly since then, confronting armed militants and leaving behind considerable destruction.

Flyers dropped in Gaza by the Israeli military on Thursday portrayed the exiled political leader of Hamas, Khaled Mashaal, as a gambler.

A cartoon drawing showed Mashaal holding three cards reading "security," "prosperity" and "future" with a message saying he was "gambling with the future of Palestine and bringing disappointment, despair and destruction" to Palestinians.