GAZA CITY, Gaza Strip (AP) -- 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.
In central Gaza City early Tuesday, at least two major explosions hit a media complex housing the offices of Hamas-run Al Aqsa television and radio. The blasts shook surrounding buildings and started a fire on the roof of the office block, one of Gaza's tallest.
AP video showed a massive flash as the first strike hit the top of the building, sending debris raining down. The building also houses offices of a number of Arab satellite television news channels.
A loud explosion was also heard within the Abu Khadra government complex in Gaza City.
The strikes came during a heavy night of bombardment, with Israeli illumination flares and repeated explosions lighting up the Gaza skyline and turning it orange.
The overnight strikes came after 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."
U.N. Secretary-General Ban Ki-moon expressed concern about the reports of Israeli forces dropping leaflets over northern Gaza Monday evening warning tens of thousands of residents to leave their homes and evacuate to Gaza City, according to a statement released by his spokesman.
"If true, this would have a further devastating humanitarian impact on the beleaguered civilians of those areas of the Gaza Strip, who have already undergone immense suffering in recent days," it said. "The United Nations agencies present in Gaza do not have the resources on the ground to cope with, or provide assistance to, an enormous extra influx of desperate people."
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.