United Nations Secretary-General Ban Ki-moon criticized Israel Monday for its role in the deaths of 44 Palestinians on U.N. premises being used as emergency shelters during the deadly 2014 conflict between Israelis and Palestinians in Gaza.

In a cover letter for an inquiry report into specific incidents during the clashes last summer, Ban said he deplored “Israeli actions” that lead to the deaths of 44 Palestinians and injuries of 227 more, who were using the U.N. buildings in Gaza as shelter from the fighting.                                                  

The report also blamed Palestinian militant groups for putting U.N. schools in Gaza in danger by hiding weapons in three locations that were not being used as shelters. Two cases were cited, when Palestinian militants "probably" fired from the schools. 

Ban called that "unacceptable."

In one case, the new inquiry says, a U.N. girls' school was hit by 88 mortar rounds fired by the Israeli Defense Forces. In another case, another girls' school was hit by direct fire from the IDF with an anti-tank projectile. A third girls' school was hit by an IDF missile.

At a fourth girls' school, the inquiry said, "no prior warning had been given by the government of Israel of the firing of 155 MM high explosive projectiles on, or in the surrounding area of the school."

The U.N. released its summary of the report but said the full 207-page report is private. The inquiry looked at 10 incidents. Ban's statement stressed that the board of inquiry "does not make legal findings" and was not tasked with addressing the wider issues of the Gaza war.

Ban ordered the inquiry in November after thousands of buildings were destroyed and at least 223 Gaza schools, either run by the U.N. refugee agency or the Islamic militant group Hamas government, were hit in the fighting. Weapons caches were found in several U.N. schools that weren't being used at the time.

At least 2,200 Palestinians died-- including 1,462 civilians—in the Gaza conflict. Israel suffered 72 casualties, including 66 military personnel and a Thai national killed by rockets and mortars fired from Gaza.

When Ban visited Gaza in October, he said the destruction was "beyond description" and "much more serious" than what he witnessed in the Palestinian territory in 2009 in the aftermath of a previous Israel-Hamas war.

Ban said Monday he has established a group of senior managers to look into the inquiry's recommendations.

Several of the world's nuclear powers gathered at the U.N. Monday to discuss progress on the landmark Nuclear Nonproliferation Treaty on disarmament. Israel is attending for the first time in two decades as an observer, with a sharp eye on the fate of nuclear talks with Iran.

The Associated Press contributed to this report.