Amnesty International has accused Israel of committing war crimes during its campaign in Gaza.

A report released by the group on Wednesday says Israel displayed “callous indifference” launching attacks on family homes in the densely populated coastal strip and in some cases its conduct amounted to war crimes. It adds that war crimes were also committed by Palestinian militants.

The 50-day war killed more than 2,100 Palestinians, most of them civilians, and 72 people on the Israeli side, all but six of whom were soldiers.

Israel’s Gaza operation came after increased rocket attacks by Gaza’s Islamic militant Hamas rulers. Israel also arrested scores of Hamas activists in the West Bank, following the abduction and murder of three Israeli teenagers.

Israel’s foreign ministry rejected the report’s findings, saying Amnesty “ignores documented war crimes perpetrated by Hamas” and had produced no evidence to back up its claims.

Amnesty says it documented eight instances in which Israeli forces attacked homes in Gaza without warning, killing “at least 104 civilians including 62 children”.

“The report reveals a pattern of frequent Israeli attacks using large aerial bombs to level civilian homes, sometimes killing entire families,” Amnesty said.

While possible military targets were identified in some cases, “the devastation to civilian lives … was clearly disproportionate”, it added.

The report charges that when it appeared to have failed to identify any military target in a Gaza residential building, Israel may have “directly and deliberately targeted civilians or civilian objects, which would constitute war crimes”.

“The report exposes a pattern of attacks on civilian homes by Israeli forces which have shown a shocking disregard for the lives of Palestinian civilians, who were given no warning and had no chance to flee,” said Philip Luther, Amnesty’s director for the Middle East and north Africa.

“Palestinian armed groups also committed war crimes, firing thousands of indiscriminate rockets into Israel killing six civilians including one child.”

The group said it had to conduct research for the report remotely as Israel denied it and other watchdogs access to Gaza.

Amnesty called on Israel and the Palestinians to “accede to the Rome statute and grant the ICC [international criminal court] the authority to investigate crimes committed in Israel and the occupied Palestinian territories”.

It called for cooperation with the UN human rights committee, which in October urged Israel to ensure an independent and impartial investigation to the Gaza war.

Israel said Amnesty had ignored “documented war crimes” by Hamas, such as the use of human shields, ammunition storage and firing at Israeli civilian population centres from within schools, hospitals, mosques and civilian neighbourhoods.

Israel was carrying out investigations into 90 incidents during the Gaza campaign, the foreign ministry said.