GAZA CITY, Gaza Strip (AP) -- Hamas and Israel blamed each other for an explosion at a Gaza park Monday that killed at least 10 Palestinians -- including nine children playing on a swing -- in a horrific scene that underscored the heavy price civilians are paying in the conflict.
Israel's military said rockets misfired by Gaza militants were responsible, while Gaza officials blamed Israeli airstrikes.
The blast took place on the first day of Eid al-Fitr, a Muslim holiday that marks the end of the holy fasting month of Ramadan.
Afterward, dozens of Palestinians crowded the spot at the park in the Shati refugee camp northwest of Gaza City, where pools of blood could be seen on the ground. Some cried out, pleading for God's mercy.
Witnesses said the youngsters had been playing on a swing set.
"The children were playing and were happy, enjoying Eid, and they got hit. Some lost their heads, others their legs and hands," Nidal Aljerbi, a witness, told The Associated Press.
Another man stood beside a pool of blood and cried: "We don't want an agreement. We don't want a cease-fire. All of us, children, women, will give our souls for God!"
In a hectic scene, Palestinians shed tears outside the doors of the morgue at Gaza City's Shifa Hospital, and relatives crammed into the hall. The bodies of three children lay on shelves in the mortuary, their clothes heavily bloodstained, their flesh torn by shrapnel.
The strikes occurred on a day of heavy fighting after a temporary humanitarian cease-fire. At the same time, international efforts to end the three-week war intensified.
The streets near the park were strewn with shattered glass from homes and shops, and the ground was marked with the bloody footprints of those who helped carry the bodies to ambulances.
Lt. Col. Peter Lerner, an Israeli army spokesman, denied Israel was involved. "This incident was carried out by Gaza terrorists whose rockets fell short," he said.
In a text message, Hamas spokesman Sami Abu Zuhri said the killings would be avenged.
"The massacre against the children in Shati refugee camp is a war crime," Zuhri said. "Such a crime is a result of the silence of the international community. This crime will not break our will, and the occupation will pay the price."
The United Nations on Monday called for an immediate cease-fire in the fighting that has killed at least 1,085 Palestinians, 52 Israeli soldiers and three civilians on the Israeli side.
The United Nations says civilians make up more than three-fourths of the dead and a majority of the wounded. Children account for at least 30 percent of the casualties, according to UNICEF, the U.N. children's agency.
In another tragic episode involving children, four Palestinian boys, cousins ages 9 to 11, were killed July 16 on a beach west of Gaza City by shellfire from a navy ship. Israel later apologized for the deaths.
Israel blames the civilian deaths on Hamas, accusing it of firing from residential neighborhoods and using civilians as human shields.
The Israeli military says it is doing its utmost to spare civilians, including issuing evacuation warnings to homes and neighborhoods that are about to be hit in Israel's air and ground operation.
Gaza is densely populated, with 1.7 million people squeezed into a small strip of land on the Mediterranean Sea, leaving little room for escape.
Over the course of the war, there have been similar instances in which each side blamed the other for strikes that have had horrific results.
Yousur Alhlou contributed to this story from Jerusalem. Associated Press journalist Dalton Bennett also contributed from the Gaza Strip.