However, the military said the cease-fire would not apply to areas where troops were still operating and where they would respond to any attack. The southern strip town of Rafah, which saw particularly heavy fighting on Sunday, was excluded from the truce, the military said.
Shortly after the cease-fire went into effect at 10 a.m. (0700 GMT), two Israeli missiles struck a beach house near Gaza City, killing one person and leaving up to 20 people missing, the Red Crescent and a Gaza health official said. The Israeli military had no immediate comment on the strike.
The Islamic Jihad group — a close ally of Gaza's militant Palestinian Hamas rulers — said its commander in the northern part of the strip, Daniel Mansour, died when an Israeli strike hit his home just before dawn.
Even though Israel has been drawing down its ground operation since the weekend, it has kept up heavy aerial, offshore and artillery bombardments of the strip. The Gaza war, now in its fourth week, has killed more than 1,800 Palestinians and more than 60 Israelis.
Hamas spokesman Sami Abu Zuhri said the group was skeptical about the Israeli truce announcement. "We do not trust such a calm and call on our people to take caution," Zuhri said.
Israel launched the military operation in Gaza on July 8 in response to weeks of heavy rocket fire. It has since carried out more than 4,600 airstrikes across the crowded seaside area. On July 17, it sent in ground forces in what it said was a mission to destroy the tunnels used by Hamas to carry out attacks inside Israel.
Since the fighting erupted, Hamas has fired more than 3,200 rockets into Israel, many of them intercepted by Israel's Iron Dome defense system. In contrast to Israel's high-tech warfare, which includes precision-guided missiles and large payload ordinance, Hamas's rocket technology remains relatively primitive and has not been as deadly.
Overnight, Israeli forces carried out new airstrikes while Israeli tanks and navy gunboats fired dozens of artillery shells, targeting houses, agricultural plots and open areas, Gaza police said. They said Israeli jet fighters destroyed three mosques, nine houses, five seaside chalets and a warehouse for construction material.
The Gaza police said Israeli navy boats also approached the northern coast of the strip and soldiers tried to land in the area. On the ground, there were clashes in the southern town of Rafah and southeast of Gaza City, they said. The Israeli military had no immediate comment.
U.N. officials say more than three-quarters of the dead in the war have been civilians, including the 10 people killed Sunday at a U.N. school that has been converted into a shelter in the southern Gaza Strip town of Rafah.
The United States said it was "appalled" by the "disgraceful" shelling and State Department spokeswoman Jen Psaki called on Israel to do "more to meet its own standards and avoid civilian casualties."
U.N. Secretary-General Ban Ki-moon called the attack on the school a "moral outrage and a criminal act" and demanded a quick investigation.
According to witnesses, Israeli strikes hit just outside the main gates of the school on Sunday. The Red Crescent, a charity, said the attack occurred while people were in line to get food from aid workers. Gaza health official Ashraf al-Kidra said in addition to the dead, 35 people were wounded.
Robert Turner, director of operations for the U.N. Palestinian refugee agency in Gaza, said the building had been providing shelter for some 3,000 people. He said the strike killed at least one U.N. staffer.
"The locations of all these installations have been passed to the Israeli military multiple times," Turner said. "They know where these shelters are. How this continues to happen, I have no idea."
Israel said that it attacked 63 sites on Sunday and that nearly 100 rockets and mortars were fired at Israel.
Al-Kidra, who also reported the casualty toll in Monday's strike on the Gaza beach house, said more than 50 Palestinians were killed Sunday, including 10 members of one family in a single strike in the southern Gaza Strip.
Israeli Prime Minister Benjamin Netanyahu has come under international pressure to halt the fighting because of the heavy civilian death toll.
U.N. shelters in Gaza have been struck by fire seven times in the latest Israeli-Hamas round of fighting. UNRWA, the U.N. agency that assists Palestinian refugees, says Israel has been the source of fire in all instances. But it also has said it found caches of rockets in vacant UNRWA schools three times.
Israel accuses Hamas of using civilian areas for cover and says the Islamic militant group is responsible for the heavy death toll because it has been using civilians as "human shields."
Enav reported from Jerusalem.
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