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 young 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.