Israeli warplanes resumed pounding Gaza, Palestinian civilians fled for shelter and rocket sirens blared in southern Israel on Friday as war resumed after a week-old truce ran out with no deal to extend it.

As the deadline lapsed, Reuters journalists in Khan Younis in southern Gaza saw eastern areas come under intensive bombardment, sending columns of smoke rising into the sky. Residents took to the streets fleeing for shelter further west.

In the north of the enclave, the main war zone for weeks, huge plumes of smoke rose above the ruins, seen from across the fence in Israel. The rattle of gunfire and thud of explosions rang out above the sound of barking dogs.

Barely two hours after the truce expired, Gaza health officials reported that 35 people had already been killed and dozens wounded in air strikes that hit at least eight homes.

Medics and witnesses said the bombing was most intensive in Khan Younis and Rafah in the southern Gaza Strip, and also targeted houses in central and northern areas.

"Anas, my son, I don't have anyone but you my son!" wailed the mother of Anas Anwar al-Masri, a boy lying on a stretcher with a head injury in the corridor of Nasser hospital in Khan Younis. "He is my only boy!"

The Israeli military announced it had "resumed combat operations" and its warplanes were striking the enclave, accusing Hamas of violating the truce first by firing rockets and failing to free all the women it was holding hostage.

"With the resumption of fighting we emphasise: The Israeli government is committed to achieving the goals of the war - to free our hostages, to eliminate Hamas, and to ensure that Gaza will never pose a threat to the residents of Israel," the office of Israeli Prime Minister Benjamin Netanyahu said.

Hamas said Israel bore responsibility for the end of the truce, for rejecting terms to free more hostages and extend it.

"What Israel did not achieve during the fifty days before the truce, it will not achieve by continuing its aggression after the truce," Ezzat El Rashq, a member of the Hamas political bureau, said on the group's website.

NEGOTIATIONS CONTINUE
The seven-day pause, which began on Nov. 24 and was extended twice, had allowed for the exchange of hostages held in Gaza for Palestinian prisoners and facilitated the entry of humanitarian aid into the shattered coastal strip.

Eighty Israeli women and children hostages were freed in return for 240 Palestinian detainees in Israeli jails, all women and teens. An additional 25 foreign hostages, mainly Thai farmworkers, were also released under parallel deals.

But mediators failed at the final hour to extend the truce by finding a formula for hostage releases to continue, possibly to include Israeli men now that fewer women and children remained in captivity.

Qatar, which has played a central role in mediation efforts, said negotiations were still ongoing with Israelis and Palestinians to restore the truce, but that Israel's renewed bombardment of Gaza had complicated its efforts.

Israel has sworn to annihilate Hamas in response to the Oct. 7 rampage by the militant group, when Israel says gunmen killed 1,200 people and took 240 hostages. Hamas, sworn to Israel's destruction, has ruled Gaza since 2007.

Israel's bombardment and ground invasion have laid waste to much of the territory. Palestinian health authorities deemed reliable by the United Nations say more than 15,000 Gazans have been confirmed killed and thousands more are missing and feared buried under rubble.

The United Nations says as many as 80% of Gaza's 2.3 million have been driven from their homes, with no way to escape the narrow territory, many sleeping rough in makeshift shelters.

Israel has imposed a total siege, and residents and humanitarian agencies say aid that arrived during the truce was trivial compared to the vast needs of so many displaced people.

U.S. Secretary of State Antony Blinken, who had met Israeli and Palestinian officials on Thursday on his third trip to the region since the war began, declined to comment on the collapse of the truce to reporters travelling on his plane.

The day before, Blinken had called on Israel to do more to protect civilians once fighting resumes. He had praised the truce and said Washington hoped it would be extended.