Israel has warned at least 100,000 Gaza residents to evacuate their homes as its aerial offensive intensifies in the aftermath of a ceasefire collapse.
People living in eastern and northern Gaza near the Israeli border have been warned through voice messages to "evacuate for the sake of your safety by 08:00 am local time [05:00 GMT]".
The inhabitants of the eastern Shuja'iyya neighbourhood in Gaza City have been given special warning.
The latest advice came after an Egypt-brokered ceasefire fell through. Although the Israeli cabinet had formally accepted the truce, Hamas did not heed it.
Had the ceasefire been upheld, it would have brought the week-long conflict, which has killed 196 Palestinians and an Israeli, to an end. Nearly 1,500 Palestinians have been injured in the Israeli offensive so far.
"We have resumed our operation against Hamas," said the Israeli Defense Forces (IDF).
Israeli Prime Minister Benjamin Netanyahu earlier said: "When there is no ceasefire, our answer is fire.
"It would have been preferable to have solved this diplomatically, and this is what we tried to do when we accepted the Egyptian proposal for a ceasefire, but Hamas leaves us no choice but to expand and intensify the campaign against it."
The renewed aerial strike has also raised fresh fears of an impending ground offensive by Israeli forces.
"A ground offensive could help combat the many tunnels in the Strip, where the Air Force is not effective," a senior Israeli military official told reporters.
Meanwhile, the UN chief has yet again urged both sides to row back from violence.
While speaking at a news conference in Haiti, UN Secretary General Ban Ki-moon said: "I have been very deeply engaged with regional and global leaders in the last few days, since the outbreak of this crisis. Even while visiting Haiti I have been speaking with world leaders.
"I appreciate key actors like the Egyptian president Sisi, and the Qatari Emir and many other leaders including the US who have been trying really hard to facilitate a ceasefire. And I was encouraged when the Israeli government has agreed to this ceasefire proposal brokered by the Egyptian president."