Israeli troops conducted house-to-house searches in the southern Gaza Strip and killed three Palestinians with tanks and air strikes early Friday, Palestinian officials said.

The overnight searches came a day after dozens of Israeli tanks rolled into Gaza and Israeli forces killed eight Palestinians in clashes and air attacks.

Three Palestinians were killed by Israeli fire in two separate incidents before daybreak Friday, hospital officials said. The Hamas militant organization said two of the casualties were Hamas members.

The Israeli army said its forces targeted 25 gunmen carrying anti-tank missiles who were planting explosives in the army's area of operations. It didn't mention casualties.

Armored forces regrouped overnight on the outskirts of the town of Rafah as the searches were under way, the army said.

Despite Israeli claims that they were pulling out of the territory, residents reported 12 Palestinians were arrested in the pre-dawn searches. Israeli forces destroyed the outer wall of one house when the owner refused to open the door.

The military said about 10 people were detained and released within a few hours.

Israeli aircraft also hit two houses in Gaza City with missiles. Residents said the military warned occupants to leave before the attacks and that no one was hurt.

Also Friday, Palestinian and Israeli officials and European monitors agreed to reopen the Gaza-Egypt border crossing on Saturday and Sunday for one-way traffic into Egypt, said Palestinian negotiator Saeb Erekat.

The crossing was intended for students to return to schools, for businessmen and for humanitarian cases, he said.

It would be the second time since the latest fighting erupted in Gaza June 25 that the terminal would be opened, but the previous time was for Palestinians returning home from Egypt. Earlier agreements to reopen the crossing from Gaza to Egypt broke down at the last minute.

Israel, which has been criticized for creating a humanitarian crisis in Gaza, said it opened another border checkpoint to allow 160 truckloads of food and medical supplies into Gaza, as well as gasoline and diesel.

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 eight to nine rockets into Israel each day, to stop.

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.