Gaza-based militants fired first after the temporary truce expired at 8 am (local time), launching 21 rockets toward Israel and marking the resumption of the month-long devastating conflict that has killed nearly 1,900 Palestinians and 67 people in Israel, including 64 soldiers.
The Israel Defence Forces said, in total, more than 35 rockets were fired at Israel on Friday.
The military said 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 said his organisation was ready for "a long war".
The Israeli military said it carried out strikes on militant targets in Gaza in response to the barrage of rockets fired after the three-day truce in the region came to an end.
A 10-year-old child was killed in an Israeli air strike, the first death since the temporary truce expired. A woman was wounded in the same attack.
Fire from Israeli tanks and Israeli gunboats was also reported from northern Gaza and at the central area of the coastal strip.
Sami Abu Zuhri, a Hamas spokesman in Gaza, said while his group did not agree to an extension of the truce, it was willing to continue the talks.
However, Israeli government spokesman Mark Regev told CNN that the resumption of rocket fire means Hamas has "broken the fundamental premise of the talks in Cairo."
The Israeli delegation arrived back from Egypt about an hour before the cease-fire ended, Israeli officials said.
Israel, which pulled its ground forces out of Gaza earlier this week, had said on Thursday that it was willing to extend the truce unconditionally.
Two militant factions -- Islamic Jihad and the Al-Nasser Salah al-Din Brigades -- who have fought alongside Hamas in Gaza under the banner of "the resistance" said they had fired rockets at Israel on Friday.
Image: Smoke rises following Israeli air strikes in Gaza City on Friday
Photo: Ahmed Zakot/Reuters
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