Gaza - The Gaza civil defense agency said Israel struck a school building sheltering displaced Palestinians on Sunday, killing at least nine people.

The Israeli military said it was "looking" into the reported air strike, the latest such attack on displacement shelters across the Gaza Strip, where the army says it is targeting Hamas militants.

The strike killed nine people and wounded several others at Asma school in Gaza City's Al-Shati refugee camp, the civil defense agency said, as rescuers were searching for more victims under the rubble.

The agency said six bodies had already been identified, including one of a girl.

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Taheer al-Rantisi said he "saw a plane destroying the building, which collapsed on top of the people" there, calling the attack "a massacre".

The Palestinians sheltering at the school building included "innocent children and elderly" people, said Rantisi.

When the strike hit, "all the people and children were torn apart", he said.

Paramedic Hussein Mohsen said the displaced people who had sought refuge there had come from Jabalia and other parts of north Gaza, where Israeli forces have carried out a sweeping assault since early October.

"This is not the first time that the Israeli occupation has targeted schools," Mohsen said.

In recent months, the military has struck several schools-turned-shelters where Israel has said Palestinian militants were operating.

In recent days, tens of thousands of Palestinians have fled Israel's major ground and air assault in northern areas of the besieged Gaza Strip. The military claims it aims to prevent Hamas militants from regrouping there.

Israel's assault has killed over 43,000 Palestinians in the last year, according to the territory's health ministry, but experts believe the true death toll may be much larger.