Israel's military confirmed it fired on a target near a UN school in the southern Gaza city of Rafah on Sunday, an attack which killed 10 Palestinians and stirred international outrage.

"The IDF (army) targeted three PIJ (Islamic Jihad) terrorists on board a motorcycle in the vicinity of an UNRWA school in Rafah," an army statement said, referring to the UN agency for Palestinian refugees.

"The IDF is reviewing the consequences of this strike" near the school where around 3,000 Palestinians were sheltering, it said.

The United Nations expressed "outrage" after what was the third such strike on one of its Gaza schools in 10 days, after 30 Palestinians were killed in the previous attacks.

UN Secretary General Ban Ki-moon called it "a moral outrage and a criminal act."

Joining a chorus of condemnation, the United States said it was "appalled" by the shelling of another UN school in Gaza and called for a "full and prompt" investigation.

State Department spokeswoman Jen Psaki stressed that "Israel must do more to meet its own standards and avoid civilian casualties."

Almost 1,800 Palestinians have been killed in Gaza and another 9,320 wounded since the start of the Israeli offensive on 8 July. Figures released by the UN humanitarian agency OCHA on 2 August gave a total of 1,525 dead.

Of the 1,196 killed whose identities could be verified, 1,033 were civilians, nearly 84 percent, OCHA said. The number includes 329 children and 187 women.

Of the Palestinians killed, 191 were members of armed groups. On the other side, 66 Israelis have been killed, including 64 soldiers, all of whom have died since the ground offensive began.

According to Israel's army figures, Palestinian factions since July 8 have fired 3,160 rockets, of which 2,483 hit Israel while 559 were intercepted by its Iron Dome anti-missile defences.

Israel says it has struck 4,626 targets across the Gaza Strip in the 27-day operation.