Palestinian houses in a Gaza City neighborhood were destroyed during Israel's war against Hamas in the Gaza Strip last summer. (Mohammed Saber/EPA)

JERUSALEM — After a dozen reports by human rights groups charging that Israel had committed war crimes during its air and ground offensive in the Gaza Strip last summer, Amnesty International on Thursday focused on the Islamist militant group Hamas and other armed factions in Gaza, which fired thousands of rockets at civilian population centers in Israel during the 50-day war.

Amnesty's conclusion: The military wing of Hamas committed war crimes, too, by indiscriminately firing unguided rockets and mortar rounds from civilian areas in Gaza at population centers in Israel.

The 70-page report found that rocket and mortar fire from the Palestinian militants also killed 13 Palestinians and six Israeli civilians.

Amnesty investigators report that a Palestinian projectile landed next to a supermarket in a refugee camp on July 28, killing 13 Palestinian civilians, 11 of them children playing in the street during a cease-fire.

In the immediate aftermath of the explosion at the al-Shati camp, Hamas spokesman Sami Abu Zuhri blamed Israeli airstrikes. In a text message to journalists, Zuhri called it a “massacre” and vowed that “this crime will not break our will.”

A spokesman for the Israel Defense Forces at the time denied firing at the neighborhood and attributed the explosions to a failed rocket launch from Gaza militants.

The Gaza war left more than 2,100 Palestinians dead; seven in 10 of them were civilians and more than 500 were children, according to Palestinian and U.N. officials. On the Israeli side, 66 soldiers and six civilians were killed, including one child.

Amnesty said the death of Daniel Tregerman, a 4-year-old Israeli boy, “clearly illustrates the tragic consequences of using imprecise weapons such as mortars on civilian areas.” His family's car was struck by a mortar round from Gaza, and he died from shrapnel wounds.

“Daniel’s little sister who was also present watched him die before her eyes,” wrote Amnesty, noting that the Hamas military wing, the Izzedine al-Qassam Brigades, asserted responsibility for the attack.

In Gaza, Hamas official Taher al-Nounou denied Amnesty's allegations, according to the Associated Press, saying the report relied on "the Israeli narrative." He told the news service that Hamas did not target civilians.

In the past, Hamas officials have pointed to the relatively low number of Israeli civilian deaths as proof that they did not target the general population. The Israelis attribute the low number of Israeli civilian fatalities to a combination of the U.S.-supplied Iron Dome air defense system, Israeli air raid sirens, and the small payloads and inexact aim of Hamas rockets.

The conclusions of the Amnesty report were not exactly news, especially in Israel.

After the report was released, Lt. Col. Peter Lerner, a top spokesman for the Israel Defense Forces, tweeted, “Wow, self-proclaimed terrorist organization carried out war crimes. Big surprise there! #Hamas must be so ashamed.”

The Palestinian militias in Gaza fired more than 4,800 rockets and 1,700 mortar rounds toward Israel, according to counts by Israel and the United Nations. Most of the rockets were relatively crude, hand-made projectiles fashioned out of water pipes that cannot be guided after they leave their launch tubes. The mortars fire at a shorter range but are often more deadly.

Many Israelis felt world opinion singled out Israel for civilian deaths in Gaza while failing to appreciate how Hamas and other factions employed human shields.

The Amnesty team pointed out that there are no bomb shelters or warning sirens in the Gaza Strip (though it is unclear how much those would have helped against unannounced strikes by Israeli armed drones, F-16s and artillery when the time from launch to target is measured in seconds).

The report condemned Palestinian militias for storing munitions in, and launching rockets from, schools, mosques, a Greek Orthodox church and at least one hospital. Amnesty also reported that the militias launched attacks and stored rockets “very near locations where hundreds of displaced civilians were taking shelter.”

The Israeli newspaper Haaretz noted that Israeli authorities refuse to allow human rights monitors to enter Gaza, including from Amnesty, making it difficult to document war crimes.

Philip Luther of Amnesty International said in a statement that both Israel and the Palestinians must cooperate with U.N. and International Criminal Court probes “to end decades of impunity that have perpetuated a cycle of violations in which civilians on both sides have paid a heavy price.”