JERUSALEM — An Israeli human rights group said Israel’s attacks on residential buildings in Gaza during the 50-day war against Hamas last summer appeared in at least some instances to violate the provisions of international law and raised grave legal concerns in others, according to a report to be published on Wednesday.

The group, B’Tselem, which is identified with the Israeli left and focuses on human rights issues in Gaza and in the Israeli-occupied West Bank, said it had investigated 70 cases in which more than 600 Palestinians were killed inside homes, a majority of them — children, women and men over the age of 60 — considered unlikely to have been involved in the fighting.

The study was at least the third by a human rights organization on the Gaza conflict, coming after reports by Amnesty International and Physicians for Human Rights-Israel, but as the first major one written by an Israeli group, it could have more resonance here than the others. It was published as prosecutors at the International Criminal Court in The Hague, at the urging of Palestinian leaders, have been conducting a preliminary inquiry into possible war crimes in Palestinian territories.