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 the hours that followed the IDF said it hit 150 targets in airstrikes overnight Monday while artillery pounded areas in the coastal enclave. Palestinian sources claimed 32 people were killed in the attacks, including the commander of Islamic Jihad’s Rahah Brigade, Ahmed Najam Abu Hamda.

The IDF ramped up its attacks after five Israeli soldiers were killed inside Israel by Palestinian gunmen who emerged from a tunnel under the border. Another four soldiers were killed, also inside Israel, in a mortar attack.

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.

UN 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 ceasefire 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 a 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 terrorists 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 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 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.

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 UN Security Council and growing pressure from the United States.

Israel has said its troops will not leave Gaza until they have demolished scores of Hamas military tunnels under the Gaza-Israel border that operatives 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 on Monday, saying “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 US frustration with the mounting number of Palestinian casualties. Hamas health officials say at least 1,072 have been killed and 6,450 wounded since July 8 while Israel says the figures include hundreds of gunmen and combatants.

The IDF says 53 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.

US 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 ceasefire 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 ceasefire as more favorable to Hamas.

Israel had accepted an Egyptian call for an unconditional ceasefire early in its Gaza campaign, but Hamas rejected the idea.

Netanyahu said Monday that Israel won’t end its offensive until Hamas’s 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.”

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.

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.