Israel's warplanes pounded Gaza, sending wounded and dead Palestinians into hospitals and residents into the streets to flee, as its war against Hamas resumed after talks to extend a week-old truce broke down.

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 road with belongings heaped up in carts, fleeing for shelter further west.

In the north of the enclave, previously the main war zone, 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.

Rocket sirens also blared across southern Israel as militants fired from the coastal enclave into towns.

Within hours of the truce expiring, Gaza health officials reported that 54 people had already been killed and dozens wounded in air strikes that hit at least eight homes.