(JTA) — Human Rights Watch accused Israel of committing war crimes by attacking three United Nations-run schools in the Gaza Strip.

The group made the accusation on Thursday when it released what it said was the first in-depth documentation of the incidents, which took place during a 50-day conflict between Israel and Palestinian militants this summer.

“Three Israeli attacks that damaged Gaza schools housing displaced people caused numerous civilian casualties in violation of the laws of war,” HRW said in the report, based on interviews with witnesses and field research in the Hamas-dominated Gaza Strip.

The organization said 45 people, including 17 children, were killed in or near the “well-marked schools” in the strikes on July 24 in the northern Gaza town of Beit Hanoun, on July 30 in Jabaliya refugee camp and on Aug. 3 in Rafah.

Human Rights Watch also said it was skeptical about the credibility of five criminal investigations announced by Israel’s military on Wednesday into its Gaza war operations.

The Israeli military said at the time that the school at Beit Hanoun was hit by errant fire and that the area around the facility had been used by Palestinian fighters to launch rockets.

The first two attacks “did not appear to target a military objective or were otherwise indiscriminate,” while the third strike, in Rafah, was “unlawfully disproportionate,” HRW wrote.

In a message on Twitter, Gerald Steinberg, the founder of the NGO Monitor group in Jerusalem, accused HRW Executive Director  Kenneth Roth of staging “obsessive attacks versus Israel” and of having “no methodology or credibility.”

Some 2,000 Palestinians were killed in seven weeks of fighting, according to the Gaza health ministry. On the Israeli side, the death toll was 73.

The United Nations Human Rights Council — which Israel has long accused of harboring an anti-Israeli agenda — last month announced the appointment of three members to its independent Commission of Inquiry to investigate purported violations of international humanitarian and human rights laws in the West Bank, east Jerusalem and the Gaza Strip since June.

Israel launched its Gaza offensive on July 8 with the declared aim of halting the cross-border rocket salvoes by Hamas.