Israel says it has resumed air strikes in Gaza after Palestinian militants fired rockets following the end of a three-day truce on Friday morning.
The Israeli army called the renewed rocket attacks "unacceptable, intolerable and short-sighted".
Palestinian militant group Hamas, which controls Gaza, earlier rejected any extension of the truce, saying Israel had failed to meet its demands.
In response to the renewal of rocket fire by Gaza terrorists at Israel, we are striking terror sites in Gaza.— IDF (@IDFSpokesperson) August 8, 2014
Every rocket fired by Hamas is meant to kill Israeli civilians. Every rocket is a war crime.— IDF (@IDFSpokesperson) August 8, 2014
A rocket that hit the Sdot Negev regional council injured a civilian moderately & a soldier lightly.— IDF (@IDFSpokesperson) August 8, 2014
WATCH: Hamas shows little care for the residents of Gaza, firing rockets from populated areas http://t.co/Wt494A0g4t— IDF (@IDFSpokesperson) August 8, 2014
Some 1,940 lives have been claimed in four weeks of fighting in Gaza.
At least 1,890 Palestinians, mostly civilians, have died, according to latest United Nations figures.
Israel, Hamas Resume Fire After 3-Day Truce in Gaza http://t.co/njWh8rArsd— Mashable (@mashable) August 8, 2014
Israel's government says 64 soldiers have been killed, along with two Israeli civilians and a Thai national. It also claims that about 900 Palestinian militants have died in the violence.
Israel launched Operation Protective Edge on 8 July with the stated aim of halting rocket fire from militants in Gaza and destroying the network of tunnels it said were used by militants to launch attacks inside Israel.
Palestinian officials told the BBC that a young boy was killed in an air strike near a mosque in Gaza City on Friday.
Correspondents say the Israeli military is also using tanks and gunboats in its offensive.
Israel senior official tells BBC ceasefire talks in Egypt are over following the resumption of hostilities in Gaza http://t.co/srB432hVlu— BBC Breaking News (@BBCBreaking) August 8, 2014
The Israel Defense Forces (IDF) earlier announced it was striking "terror sites across the Gaza Strip" in response to renewed rocket attacks on Israeli cities.
Militants began firing missiles from Gaza shortly before the ceasefire ended at 08:00 local time (05:00 GMT).
The IDF said more than 35 rockets were fired at Israel on Friday morning.
The military added that its Iron Dome anti-missile shield had intercepted three rockets, while the remaining ones fell on open ground.
The violence resumed after Egyptian-brokered talks between Israel and Palestinian factions hit a deadlock.
Negotiators in the Egyptian capital, Cairo, were working against the clock on Thursday to persuade the two sides to extend the 72-hour ceasefire and agree a long-term deal.
But Hamas said Israel had failed to meet its key demands, including the lifting of the blockade of Gaza, the release of prisoners and the end of the Israeli offensive.
The group also rejected Israel's call for the demilitarisation of Gaza. A Hamas spokesman warned his organisation was ready for "a long war".
However, the group said Palestinian factions were willing to continue the Cairo talks despite the fresh clashes.
But Israeli government officials have announced that they are pulling out of the talks, stressing that they will not "negotiate under fire".
A senior official told the BBC that the Israeli delegation had left Cairo earlier on Friday.
"Hamas is now continuing to fire towards Israeli civilians, while Israel fully respected the ceasefire and announced it is ready to extend it," he said.
On Thursday, the human rights group Amnesty International called for an investigation into what it said was mounting evidence that Israeli forces had deliberately attacked hospitals and health professionals in Gaza. The attacks have left at least six medics dead.