In New York, the U.N. Security Council called unanimously for a cease-fire, while Britain's foreign minister said he will discuss cease-fire efforts with his American, French and German counterparts on Sunday.
So far, neither Israel nor Gaza's Hamas rulers have signaled willingness to stop.
Israel has carried out more than 1,200 air strikes this week to try to diminish Hamas' ability to fire rockets at Israel, and the chief military spokesman, Brig. Gen. Motti Almoz, said Saturday there would be more strikes, especially in northern Gaza near the Israeli border.
"We are going to attack there with great force in the next 24 hours due to a very large concentration of Hamas efforts in that area," he said. Late Saturday, the military said it was ordering Palestinians in northern Gaza to evacuate "for their own safety."
Gaza's Interior Ministry urged residents in the area to ignore Israel's warnings and to stay in their homes, saying the announcement was Israeli "psychological warfare" and an attempt to create confusion.
Shortly after the Israeli announcement, an Israeli warplane struck the home of the Gaza police chief, Taysir al-Batsh, killing at least 18 people and wounding 50, said Health Ministry official Ashraf al-Kidra. He said worshippers were leaving the mosque after evening prayers at the time of the strike and that some people are believed to be trapped under the rubble.
Meanwhile, Hamas, the Islamic militant group that controls Gaza, has fired nearly 700 rockets and mortars at Israel this week and said it wouldn't be the first to cease fire.
In a sign that the conflict might widen, Israel fired into Lebanon late Saturday in response to two rockets fired from there at northern Israel. There were no injuries or damage, but Israel fears militant groups in Lebanon may try to open a second front.
Israel has said it's acting in self-defense against rockets that have disrupted life across much of the country. It also accuses Hamas of using Gaza's civilians as human shields by firing rockets from there.
Critics said Israel's heavy bombardment of one of the most densely populated territories in the world is itself the main factor putting civilians at risk. Sarit Michaeli of the Israeli human rights group B'Tselem said that while using human shields violates international humanitarian law, "this does not give Israel the excuse to violate international humanitarian law as well."
The Israeli military said it has targeted sites with links to Hamas, including command centers, and that it issues early warnings before attacking. But Michaeli said civilians have been killed when Israel bombed family homes of Hamas militants or when residents were unable to leave their homes quickly enough following the Israeli warnings.
Before dawn Saturday, an Israeli missile hit the Palestine Charity, a center for the physically and mentally disabled in the northern Gaza town of Beit Lahiya, said its director, Jamila Alaiweh.
The center is home to nine patients, including four who were spending the weekend with their families away from the center, said Alaiweh. Of the remaining five, two were killed in the strike and three suffered serious burns and other injuries, the director said. A caregiver was also injured, she added.
The director said one of the women killed had cerebral palsy and the other suffered had severe mental handicaps. Among the three wounded patients were a quadriplegic, one with cerebral palsy and one with mental disabilities, she said.
The missile destroyed the bottom floor of the two-story building. Rescuers sifted through the pile of rubble, pulling out a folded-up wheelchair and a children's workbook.
An Israeli military spokesman, Lt. Col. Peter Lerner, said he was looking into the incident.
An army statement said that from Friday morning to Saturday morning, Israel targeted 158 targets "affiliated with Hamas terrorism" in Gaza, including dozens of rocket launchers and a mosque where Hamas stored rockets and weapons.
Israel also targeted several civilian institutions with presumed ties to Hamas, widening its range of targets. Palestinian officials said this included a technical college, a media office, a small Kuwait-funded charity and a branch of an Islamic bank.
The Israeli military did not mention these institutions in its statement Saturday, saying only that in addition to the military targets, it struck "further sites."
Al-Kidra, the health official, said Israeli strikes raised the death toll there to more than 150, with over 920 wounded. Among the dead was a nephew of Ismail Haniyeh, a top Hamas leader, who was killed in an airstrike near his home, Hamas officials said.
Though the exact breakdown of casualties remains unclear, dozens of the dead also have been civilians. Israel has also demolished dozens of homes it says are used by Hamas for military purposes.
"Am I a terrorist? Do I make rockets and artillery?" screamed Umm Omar, a woman in the southern town of Rafah whose home was destroyed in an airstrike. It was not immediately known why the building was targeted.
At Shifa Hospital in Gaza City, 4-year-old Shayma al-Masri was in stable condition Saturday with shrapnel injuries to her upper body.
Her mother, a 17-year-old brother and a 14-year-old sister were killed earlier this week when two missiles struck as the family walked in their neighborhood, said Shayma's aunt Samah. The girl is left with her father and three older brothers.
The aunt, addressing Israeli mothers, said children are precious on both sides of the conflict.
"You can hide your children in the bomb shelters when you need them, but where do I hide her (Shayma)?" she said. "When the child comes to hide in my arms and I find the entire house falling on top of us what do I do then? Just like you fear for yourselves we fear for ourselves too. Just like you fear for your children we fear for our children too."
The "Iron Dome," a U.S.-funded, Israel-developed rocket defense system, has intercepted more than 130 incoming rockets, preventing any Israeli fatalities so far. A handful of Israelis have been wounded by rockets that slipped through.
On Saturday, air raid sirens went off in Jerusalem and Tel Aviv, Israel's two largest cities, both located nearly 50 miles (80 kilometers) from Gaza. Most of the rockets were intercepted or fell in open areas, though one landed near the Palestinian city of Hebron in the West Bank. A house was damaged but there were no injuries.
The frequent rocket fire has disrupted daily life in Israel, particularly in southern communities that have absorbed the brunt of it. Israelis mostly have stayed close to home. Television channels air non-stop coverage of the violence and radio broadcasts are interrupted live with every air raid siren warning of incoming rockets.
The frequent airstrikes have turned bustling Gaza City into a virtual ghost town during the normally festive monthlong Ramadan holiday, emptying streets, closing shops and keeping hundreds of thousands of people close to home where they feel safest from the bombs.
The offensive marks the heaviest fighting since a similar eight-day campaign in November 2012 to stop Gaza rocket fire. The outbreak of violence follows the kidnappings and killings of three Israeli teenagers in the West Bank, and the kidnapping and killing of a Palestinian teenager in an apparent revenge attack.
Israel has massed thousands of troops along the border in preparation for a possible ground invasion, with soldiers atop vehicles mobilized and ready to move if the order arrives.
In London, Foreign Minister William Hague of Britain, a close Israeli ally, said he had spoken to his Israeli counterpart and called for an "immediate de-escalation" and expressed his "deep concern" about civilian casualties.
The Arab League said foreign ministers from member states will hold an emergency meeting in Cairo on Monday.