Read: Gaza's sole power plant knocked out by Israeli strike: official
By the time dawn broke on the second day of the Muslim holiday of Eid al-Fitr, at least 24 people had been killed, among them nine women and four children, medics said, as the conflict, now in its 22nd day, showed no sign of letting up.
With the Palestinian death toll passing the 1,100 mark, Iran's supreme leader accused Israel of committing "genocide in Gaza, and demanding the Islamic world arm those Palestinians involved in fighting the Jewish state.
In a speech Tuesday marking the Eid festival, Ayatollah Ali Khamenei said Israel was acting like a "rabid dog" and "a wild wolf" and causing a human catastrophe in Gaza, where people should be helped to defend itself.
"The world and especially the Islamic world should arm ... the Palestinian people," he said.
Following a relatively quiet weekend, the violence surged again on Monday, drawing increasingly urgent international demands for an end to the fighting
"In the name of humanity, the violence must stop," pleaded UN secretary general Ban Ki-moon.
But the calls appeared to be falling on deaf ears, with Israeli Prime Minister Benjamin Netanyahu warning Monday it would be "a lengthy campaign" that would not end before troops destroyed cross-border tunnels used for staging attacks on southern Israel.
"Israeli citizens cannot live with the threat from rockets and from death tunnels -- death from above and from below," he said.
Read: Gaza militants kill five Israeli soldiers after infiltrating through tunnel
Israeli soldiers of the 155mm artillery cannons unit fire towards the Gaza Strip from their position near Israel's border with the coastal Palestinian enclave. (AFP photo)
New Gaza exodus
On the ground, hundreds of Palestinians could be seen leaving their homes after the army warned residents of five areas to flee and take refugee in central Gaza City, an AFP correspondent said.
Many headed for already-cramped UN schools in the north, where children ran barefoot around a dirty school yard alongside stinking piles of rubbish.
"We came yesterday after the army warned us to leave," said 46-year-old Ghassan Abed who fled from his home in the northern town of Beit Lahiya with his wife and six children.
"About 200 people just from our street have fled," he said.
UN statistics published Monday showed 215,000 Palestinians had already fled their homes, with 170,461 staying in 82 of the agency's schools.
Read: Violence soars in Gaza as world pleads for truce
Also Tuesday, Israel confirmed another five soldiers had been killed in an ambush by militants on Monday evening after they sneaked into southern Israel by a tunnel.
Their deaths raised to 53 the total number of soldiers killed since the operation began on July 8. Another three civilians have been killed by rocket fire - two Israelis and a Thai national - raising the overall toll on the Israeli side to 56.
Watch: Massive explosions from airstrikes in Gaza
On Tuesday, several tank shells struck Gaza's sole power plant, causing damage and a fire, bringing it grinding to a halt, a senior official with the power authority said.
Another air strike targeted the home of top Hamas leader Ismail Haniya in Gaza City's Shati refugee camp, officials said.
Read: Gaza crisis: UN Security Council calls for 'unconditional ceasefire'
Read: Is India ignoring Palestine to humour Israel?
A deceptive calm
Tensions rose sharply on Monday after a shell landed inside the Shifa hospital compound in Gaza City, followed by a blast at a children's playground in the city's Shati refugee camp, that killed 10, eight of them children.
Residents in Shati said an F-16 fired several missiles at a motorised rickshaw in a claim denied by the Israeli army, which also said it had not targeted the hospital.
"We have not fired on the hospital or on Shati refugee camp," Major Arye Shalicar told AFP, saying the army had footage showing militants firing at Israel but the missiles falling short and striking targets inside Gaza.
Shortly afterwards, a mortar killed four soldiers near a kibbutz in southern Israel, the army said, indicating another soldier had been killed in action in southern Gaza.
As the violence soared, top diplomats from Britain, France, Germany, Italy and the United States pledged to "redouble their efforts" and step up the pressure to persuade the sides to accept a truce.
And Palestinian president Mahmud Abbas was expected to visit Cairo with representatives of Hamas and Islamic Jihad, another militant group, for fresh talks with the Egyptians on ending the violence in Gaza, a senior source in Ramallah told AFP, without saying when.
Pro-Palestine demonstrators shout slogans as they wave a Palestinian flag in protest against Israel's military action in Gaza, at Avenue Habib Bourguiba in Tunis. (Reuters photo)
HT Edit: Bombing civilians is wrong: an Israeli soldier draws the moral line
Full coverage: Gaza under attack