Authorities in Hamas-ruled Gaza accuse Israeli forces of a "heinous massacre" with a strike on a school they say killed almost 30 people, many of them children.

Israeli strikes have killed more than a dozen people in the Gaza Strip as Israel sends more ground troops into the Palestinian territory to ramp up its offensive against Hamas.

Israel’s military says an initial investigation into the killing of 15 emergency workers in south Gaza last month showed that the incident occurred "due to a sense of threat." But video and eyewitness evidence suggest a different story.