Human Rights Watch has accused Israel and Palestinian militants of apparent war crimes during an intense outbreak of fighting over the course of 11 days in May.
The rights organization said on Tuesday it had investigated three Israeli attacks in which 62 Palestinian civilians were killed in Gaza. There were no obvious military targets nearby, it said.
Palestinian militants also committed unlawful attacks that targeted civilians, the group said, noting that more than 4,360 rockets and mortar shells were fired at Israeli population centres.
Israel denies accusations of war crimes and has repeatedly said it does everything possible to avoid civilian casualties. Both Hamas, which rules the Gaza Strip, and Israel accuse each other using their own people as human shields.
The UN Human Rights Council condemned the actions of both sides back in May. Its members decided to launch a probe into possible war crimes committed during the military escalation.
The Health Ministry in Gaza said 255 Palestinians died. In Israel, there were 13 fatalities.
Hamas is classified as a terrorist organization by Israel, the United States and the European Union.