“The repeated, disproportionate attacks on homes indicate that Israel’s current military tactics are deeply flawed and fundamentally at odds with international humanitarian law,” said Philip Luther, director of Amnesty’s Middle East and North Africa program, said in a statement accompanying the report, which was released just after midnight.

Israel on Tuesday reopened its crossing points into Gaza, two days after closing them in response to a rocket having been fired from Gaza into Israel on Friday night, a violation of the Aug. 26 cease-fire. Robert Serry, the United Nations special coordinator for the Middle East peace process, announced Tuesday that its reconstruction effort had begun in Gaza, with 700 families being allowed to purchase materials to repair their homes by Monday evening.

But Robert Turner, the Gaza director of the United Nations Relief and Works Agency, told reporters Tuesday that he did not yet see a functioning Palestinian government on the ground, and reiterated concerns over Israel’s continued restrictions on Gaza travel and trade. Reuters quoted Mr. Turner, whose agency runs education, health and other services for 70 percent of Gaza’s population, as saying, “If we do not have political stability, I think if we do not have a national Palestinian government, I think if we do not have at least an easing of the blockade, yes, there will be another war.”

The Amnesty report, the most detailed yet on the war by an international group, calls for both Israel and the Palestinians to join the International Criminal Court so it can prosecute cases from this summer, and urges Israel to participate in an inquiry by the United Nations Human Rights Council that it has so far boycotted out of concern for predetermined bias.

Amnesty said its employees had been barred by Israel from entering Gaza since 2012, and thus relied on two fieldworkers who visited the site of each bombing multiple times. Military experts enlisted by Amnesty reviewed photographs and videos from the sites, according to the report, and surmised that 1- and 2-ton bombs were used.

The bulk of the report comprises survivors’ accounts.

“We couldn’t hear the kids, their voices had completely gone — that’s when I realized they were all dead,” Khalil Abed Hassan Ammar, a doctor, is quoted as saying about the July 20 strike on his home in Gaza City. “I only recognized Ibrahim, my eldest child, when I saw his leg and the shoes he was wearing. I had bought them for him two days before.”