Israel hit a Gaza school on Thursday in an airstrike that it said targeted and killed Hamas fighters inside, while a Hamas official said 40 people including women and children were killed as they sheltered in the U.N. site.

Ismail Al-Thawabta, the director of the Hamas-run government media office, rejected Israel's assertion that the U.N. school in Nuseirat, in central Gaza, had hidden a Hamas command post.

"The occupation uses ... false fabricated stories to justify the brutal crime it conducted against dozens of displaced people," Thawabta told Reuters.

Israel's military said it had taken steps to protect civilians before its fighter jets carried out a "precise strike", circulating satellite photos highlighting two parts of a building where it said the fighters were based.

"We're very confident in the intelligence," military spokesperson Lt Col. Peter Lerner told a briefing with reporters, accusing Hamas and Islamic Jihad fighters of deliberately using U.N. facilities as operational bases.

He said 20-30 fighters were located in the compound, and many of them had been killed, but had no precise details as intelligence assessments were being carried out. "I'm not aware of any civilian casualties and I'd be very, very cautious of accepting anything that Hamas puts out," he said.

The school, run by the U.N. Palestinian refugee agency (UNRWA), may have been hit several times, said the agency's communications director, Juliette Touma.

She said she could not confirm the death toll at this stage. Media in Hamas-run Gaza had earlier put the toll at 35-40. Thawabta and a medical source said 40 had been killed, including 14 children and nine women.

Israel announced a new military campaign in central Gaza on Wednesday as it battles fighters relying on hit-and-run insurgency tactics. It says there will be no halt to fighting during ceasefire talks, which have intensified since U.S. President Joe Biden outlined a proposal on Friday.

Source: Reuters