Israeli jets intensified attacks on central Gaza on Sunday, residents and medics said, as battles raged through the rubble of towns and refugee camps in a war Israeli Prime Minister Benjamin Netanyahu said would take "many more months" to end.

Netanyahu's comments signal no let-up in a campaign that has killed many thousands and levelled much of Gaza, while his vow to restore Israeli control over the enclave's border with Egypt raises new questions over an eventual two-state solution.

The Israeli military will release some reservists who were called up to fight Hamas in Gaza, a move it said on Sunday would help the economy as the country prepares for a prolonged war.

Air strikes pounded al-Maghazi and al-Bureij in the centre of Gaza, killing 10 people in one house and driving more to flee to Rafah on the border with Egypt from front lines where Israeli tanks are battling Hamas fighters.

Rockets fired from Gaza raced toward central Israel overnight, triggering sirens throughout the central and southern parts of the country. Israeli media carried footage of numerous interceptions. There were no reports of any direct hits.

Hamas' armed wing said the barrage was in response to "massacres against civilians" in Gaza.

A Red Crescent video published on Sunday showed rescuers working in the dark to carry an injured child from smoking rubble in central Gaza. Six people died in a strike on the village of al-Mughraqa outside Gaza City, health officials said. A separate strike on a house in Khan Younis killed one person and wounded others, they added.