More than 1,000 Palestinians have been killed by Israeli forces since May while trying to get food in Gaza, mostly near food sites run by an American contractor, the U.N. human rights office said.

Twenty Palestinians were killed Wednesday in the crush of a crowd at a food distribution site run by an Israeli-backed American organization in the Gaza Strip, the group said, the first time it has acknowledged deadly violence at its operations.

At least 85 Palestinians were killed while seeking aid in one of the deadliest days for aid-seekers since the war began, Gaza's Health Ministry said.