Gaza's civil defence agency said on Saturday an overnight Israeli strike killed nine members of a Palestinian family including six children in the southern city of Rafah.

Five children aged one to seven and a 16-year-old girl were among the dead, along with two women and a man, according to the city's Al Najjar hospital.

"Nine martyrs including six children were pulled out from the rubble after Israeli air forces struck a house of the Radwan family in Tal al-Sultan in Rafah," Gaza Civil Defence agency spokesman Mahmud Bassal said in a statement.

Outside the hospital witnesses saw people grieving over small body bags. A woman stroked a dead boy's forehead as planes rumbled overhead.

"People were sleeping peacefully," said neighbour Abu Mohammed Ziyadah.

"As you can see, there were no militants, not even male adults, except for the head of the family. They were all women and children."

Soon after the war in Gaza began on October 7, Israel told Palestinians living in the north of Gaza to move to "safe zones" in the territory's south such as Rafah.

But Israeli Prime Minister Benjamin Netanyahu has since vowed to invade the city, where around 1.5 million people – more than half the territory's population – are sheltering.

Israel has for two months threatened to send troops in against Hamas militants, but even without such an operation Rafah is under regular bombardment.

Bassal said the Israeli army struck several areas in Rafah overnight, including the Salam neighbourhood where one person was killed and several wounded. He said the army hit a house and a nursery school.

"It has been a very hard night on Rafah," he said. (AFP)