The UN secretary general has ordered an investigation into an incident in which Palestinian militants fired mortars at Israel from a UN-run school in Gaza.
Ban Ki-moon condemned the abuse of UN facilities and described it a "serious violation of the UN's privileges and immunities", a spokeswoman said.
Israeli military aircraft filmed the mortars being fired from the school's playground in Beit Hanoun last week.
The UN has already complained about the incident to the authorities in Gaza.
The coastal territory has been controlled by the Islamist movement, Hamas, since it seized control from the rival Fatah group of Palestinian Authority President Mahmoud Abbas in June.
The Israeli military's video of the incident on 29 October, taken from the air using thermal imaging equipment, shows three figures firing mortars outside the school run by the UN agency for Palestinian refugees, Unrwa, in Beit Hanoun.
Unrwa commissioner-general Karen Koning AbuZayd said the school had been evacuated earlier in the day because of an Israeli military incursion nearby.
"This is a problem when we're not there, what happens to our schools," Ms AbuZayd told a news conference on Wednesday.
"We've complained frequently to both sides - to the Israelis when the IDF (Israel Defense Forces) comes in and use our schools for interrogating people, and also to the Palestinians whenever anybody also violates our installations," she added.
A spokeswoman for the UN secretary-general said he had asked Unrwa to fully investigate the incident.
"The secretary-general condemns this abuse of UN facilities, which is a serious violation of the UN's privileges and immunities," Marie Okabe said.
"He calls on all involved in this conflict to avoid actions that endanger the lives of civilians, especially children, and that put at risk Unrwa's ability to carry out its humanitarian mission."
Rockets are fired from the Gaza Strip on an almost daily basis by Palestinian militants, who say they are responding to continued Israeli aggression.
The Israeli government has responded by declaring the coastal territory a "hostile entity" and stepping up economic and political sanctions.
Last week, Israel's attorney general intervened to suspend government plans to restrict electricity supplies to Gaza's civilian population, although fuel restrictions have already been initiated. The UN has called the sanctions punitive and unacceptable.