GAZA CITY, Gaza Strip -- Signaling an escalation of Israel's Gaza operation, Prime Minister Benjamin Netanyahu told Israelis Monday to be ready for a "prolonged" war, and the military warned Palestinians in three large neighborhoods to leave their homes and head immediately for Gaza City.
The warnings came on a day of heavy Hamas-Israeli fighting in which nine children were killed by a strike on a Gaza park where they were playing, according to Palestinian health officials -- a tragedy that each side blamed on the other.
Israeli tanks also resumed heavy shelling in border areas of Gaza, killing five people, including three children and a 70-year-old woman, and wounding 50 in the town of Jebaliya, which was among the areas warned to evacuate, the Red Crescent said.
Many Jebaliya residents said they did not dare attempt an escape. Sufian Abed Rabbo said his extended family of 17 had taken refuge under the stairway in their home.
"God help us. We have nothing to do but pray," the 27-year-old told The Associated Press by phone. "I don't know who left and who stayed, but in our street, we are all very scared to move."
Later Monday, Israeli forces fired a large numbers of flares over Gaza City, turning the night sky a bright orange.
The latest bloodshed came despite mounting international calls for a cease-fire and followed failed attempts by both sides to agree to even a lull in fighting of several hours for the start of the three-day Muslim holiday of Eid el-Fitr that marks the end of Ramadan.
The Hamas-run health ministry said 10 people, including nine children under the age of 12, were killed and 46 wounded in the blast at a park in the Shati refugee camp on the outskirts of Gaza City.
Each side blamed the other.
Lt. Col. Peter Lerner, an Israeli military spokesman, said the explosion was caused when a rocket launched by Gaza militants misfired and landed in the park. Palestinian police and civil defense said an Israeli missile hit as children were playing on a swing set.
"The children were playing and were happy, enjoying Eid, and they got hit," said Nidal Aljerbi, a witness.
After three weeks of bloodshed, both Israel and Hamas are holding out for bigger gains and a cease-fire remains elusive, despite an appeal by the U.N. Security Council and growing pressure from the United States.
Israel says its troops will not leave Gaza until they have demolished scores of Hamas military tunnels under the Gaza-Israel border that militants use to infiltrate Israel and smuggle weapons. Hamas says it will not cease fire until it receives international guarantees Gaza's 7-year-old border blockade by Egypt and Israel will be lifted.
Netanyahu defended the Gaza air and ground offensive, saying in a televised speech Monday that "there is no war more just than this."
Israel has said it is defending its citizens against attack from Gaza by hitting Hamas rocket launchers, weapons storage sites and military tunnels. However, there is growing U.S. frustration with the mounting number of Palestinian casualties -- at least 1,072 killed and 6,450 wounded since July 8, the vast majority civilians, according to Hamas health officials.
The Israeli military says 52 soldiers have been killed, including four killed Monday in a mortar attack on southern Israel. Two Israeli civilians and a Thai citizen working in Israel also have been killed.
President Barack Obama and Secretary of State John Kerry have been pressing Israel to accept an immediate and unconditional humanitarian cease-fire.
The Obama administration pushed back Monday against a torrent of Israeli criticism over Kerry's latest bid to secure a cease-fire with Hamas, accusing some in Israel of launching a "misinformation campaign" against the top American diplomat.
"It's simply not the way partners and allies treat each other," State Department spokeswoman Jen Psaki said.
Her comments were echoed by the White House, where officials said they were disappointed by Israeli reports that cast Kerry's efforts to negotiate a cease-fire as more favorable to Hamas.
Israel had accepted an Egyptian call for an unconditional cease-fire early in its Gaza campaign, but Hamas rejected the idea.
Netanyahu said Monday that Israel won't end its offensive until Hamas' network of tunnels under the Gaza-Israel border has been neutralized. "We need to be ready for a prolonged campaign," he said. "We will continue to act aggressively and responsibly until the mission is completed to protect our citizens, soldiers and children."
Hamas spokesman Sami Abu Zuhri responded defiantly. "His threats do not scare Hamas or the Palestinian people, and the occupation will pay the price for the massacres against civilians and children," he said.
Israel's last major Gaza invasion ended in January 2009 after 23 days, one-third of that time with troops on the ground. Already, the current ground operation, which began 11 days ago, has lasted longer than the one in 2009.
In recent days, Israeli leaders have debated whether to withdraw from Gaza after the tunnels are demolished, or to expand the ground operation to deliver a more painful blow against Hamas. Those in favor of an escalation have argued that unless Hamas is toppled and disarmed, a new round of Israel-Gaza fighting is inevitable. Opponents say attempting to reoccupy densely populated Gaza, even if for a short period, could quickly entangle Israel politically and militarily and drive up the number of dead.
In his remarks Monday, Netanyahu didn't let on which way he is leaning. However, he insisted that "preventing the arming of terror groups and demilitarizing Gaza must be part of any solution," indicating that Israel's aims are broader than initially stated.
For now, ground forces have largely operated on the edges of Gaza.
The Israeli military has said it has located 31 tunnels, is aware of the existence of 10 more and has so far demolished close to 20.
Gaza militants have repeatedly used the tunnels to sneak into Israel, including on Monday when several infiltrated into southern Israel. The army said one Hamas militant coming through a tunnel was killed in a firefight, but that searches in the area were continuing.
The Hamas military wing said nine of its fighters infiltrated and attacked an army post.
After three weeks of battle, "our fighters still have a lot of surprises in store for the leaders of the occupation and their elite soldiers," the group said in a statement.
The blast at the Gaza park occurred within minutes of a separate strike Monday afternoon on nearby Shifa Hospital, Gaza City's largest medical facility. Several people were wounded in the blast near one of the hospital's outpatient clinics, Hamas health officials said.
Lerner, the army spokesman, denied Israel was involved in the two attacks. "This incident was carried out by Gaza terrorists whose rockets fell short and hit the Shifa Hospital and the Beach (Shati) camp," he said, adding that the military had identified 200 "failed launchings" so far.
Early Tuesday, the military released aerial photographs that it said showed the paths of two misfired Hamas rockets it said hit the park and Shifa Hospital. It said the rockets were detected by Israeli military radar and sensors.
Gaza's police operations room and civil defense department blamed the attacks on Israeli airstrikes.
Gaza's Interior Ministry spokesman Eyad al-Bozum said he believes that shrapnel found in the dead and wounded is evidence of Israel's role in the incident.