An Israeli air strike killed a Palestinian in Gaza before a second bombing killed eight more people at the funeral hours later, health officials said on Friday.
Twenty more people were injured when the second strike hit mourners during the funeral procession in Nuseirat refugee camp.
The first victim had been killed hours earlier on Friday in the same area of central Gaza.
Three Palestinians were killed in separate Israeli air strikes elsewhere in Gaza, bringing the day's death toll to at least 12, medics said.
Hamas condemned the Nuseirat strike as a “brutal massacre” of mourners and urged peace negotiators, as well as the UN, to act to halt Israeli attacks in Gaza.
Asked about the attack in Nuseirat, the Israeli military said it struck a cell belonging to the Palestinian Islamic Jihad militant group, which holds sway in parts of the enclave along with Hamas.
The military said it was “aware of the claims that several uninvolved individuals were harmed as a result of the strike”.
Residents in an area east of Deir Al Balah in central Gaza said Israeli forces used drones to broadcast orders to leave their homes. Some families fled for safety.
The deaths add to a toll of more than 1,100 Palestinians, mostly civilians, killed by Israeli attacks since an October ceasefire between Israel and Hamas militants took effect, according to Gaza health officials.
The truce halted major fighting but has not stopped near-daily Israeli strikes. Israel says it is targeting militants. Four Israeli soldiers have been killed in Gaza over the same period.
Conflict monitor Acled, a US research group that tracks political violence, said Israeli air strikes against Hamas and other militants rose to more than 40 in June, the highest monthly total since the ceasefire.
Other strikes hit people near the line dividing the two sides, killing and injuring civilians, including women and children, it said.
