Saturday morning in Gaza City, desperate Palestinians seeking refuge in a school complex awoke to a catastrophic blast.

An Israeli air strike hit the Al-Taba'een school in the Daraj neighbourhood in the east of the city, where local authorities said thousands displaced in the 10 month long Gaza war were sheltering.

Photos and video from the site are confronting, with images of devastating destruction broadcast around the world.

But there is a dispute as to the severity of the strike, in what Palestinian officials are describing as one of the deadliest attacks of the war so far.

The fact an air strike occurred at all is not in dispute — Israel has confirmed it targeted the school complex, with a mosque nearby.

Three missiles tore through the building as people slept, washed and performed dawn prayers before sunrise on Saturday morning.

The exact number of people killed is unknown — local civil defence authorities are saying more than 90 people have been killed and dozens more injured as a result of the strike.

Witnesses to the attack and its aftermath have described, in graphic detail, the human toll of the strike — mangled bodies torn apart in the blast, many unidentifiable and incomplete.

The United Nations says it is the 21st strike on a school since July, and that 477 out of 564 schools in Gaza have been damaged or destroyed between October 7 and early July this year.

Israel says it had intelligence that Islamic militants were hiding among civilians at the school, and that it was being used as a command centre for Hamas and other groups fighting Israeli forces.

In the hours after the strike, Israeli security services and the defense force said at least 19 Hamas and Islamic Jihad fighters had been identified as killed in the blast.