Amnesty International said in a report Thursday that Palestinian organizations had committed war crimes during the 2014 Gaza-Israel conflict, by killing both Israeli and Palestinian civilians using indiscriminate projectiles.
The report from the human rights group comes after two other reports issued in late 2014 that accused Israel of war crimes for attacks on multistory civilian buildings and attacks on Palestinian residential homes during the war.
The 50-day Gaza war left more than 2,100 Palestinians dead, mostly civilians, according to Palestinian and U.N. officials. On the Israeli side, 66 soldiers and six civilians were killed.
Palestinian fighters, including the armed wing of Hamas, launched unguided rockets and mortars which cannot be aimed at a specific target and are a breach of international law, the human rights group said.
Six civilians in Israel were killed in such attacks, and 13 Palestinian civilians were killed when a Palestinian projectile launched from the Gaza Strip apparently landed in a Gaza refugee camp.
Palestinians have claimed that the Israeli military was responsible for that attack, but Amnesty International said an independent munitions expert examining the evidence on the group's behalf concluded that a Palestinian rocket was responsible.
Hamas officials did not immediately respond to requests for comment.
The report also alleged other international humanitarian law violations during the conflict, including Palestinian militant groups' storing munitions in civilian buildings and United Nations schools, and launching attacks near locations where hundreds of displaced civilians were taking shelter.
"The devastating impact of Israeli attacks on Palestinian civilians during the conflict is undeniable, but violations by one side in a conflict can never justify violations by their opponents," said Philip Luther of Amnesty International.
Luther called on both Israeli and Palestinian authorities to 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."
Amnesty International in November accused Israel of committing war crimes during its military operation in Gaza, saying Israeli forces had displayed "callous indifference" in attacks on family homes in the densely populated coastal strip. Israel's government dismissed the report, the latest in a series by human rights organizations questioning Israeli tactics in Gaza.
A report by Human Rights Watch (HRW) in September also accused Israel of committing war crimes in the course of its Gaza operation, citing three attacks on or near United Nations-run schools converted to house Palestinians displaced by shelling.
HRW said it investigated strikes at three separate locations in the besieged enclave, noting that at least 45 people were killed in the raids on the schools.
The HRW report comes a day after the Israeli military announced it had launched its own probe into cases involving Palestinian civilian casualties during the war, including the shelling of a U.N. school.
Al Jazeera with The Associated Press