Air strikes on Gaza killed 23 people, including an eight-year-old child and two teenagers, and Israeli forces killed four Hamas militants who staged a beachfront assault on an army base just north of the besieged Strip.
In the worst strike, a missile slammed into a house in the southern city of Khan Yunis after people had reportedly formed a human shield to protect it, killing seven people.
Emergency services spokesman Ashraf al-Qudra told AFP two teenagers were among the dead and that at least another 25 people were wounded.
An eight-year-old child wounded in the strike later died of his injuries.
Witnesses said an Israeli drone fired a warning flare, prompting relatives and neighbours to gather at the house as a human shield and that, shortly afterwards, an F-16 warplane fired a missile that levelled the building.