BAGHDAD — U.N. officials said Thursday they will be looking into whether war crimes and crimes against humanity were committed in recent shootings of Iraqi civilians by U.S.-hired contractors, and they urged U.S. authorities to hold private security firms accountable for unjustified killings of Iraqis.

"For us, it's a human rights issue," said Ivana Vuco of the U.N. Assistance Mission to Iraq. "We will monitor the allegations of killings by security contractors and look into whether or not crimes against humanity and war crimes have been committed. "

Said Arikat, the U.N. mission spokesman, urged the U.S. government to hold those involved in indiscriminate shootings of Iraqis "to the bar, to apply the rules of engagement and prosecute them."

The comments came as UNAMI released its quarterly human rights report in Baghdad, dealing mainly with the country's deepening humanitarian crisis but also noting the shooting incidents involving guards protecting U.S. government-funded work.

Although the United Nations holds little influence in daily matters in Iraq, it is viewed by most Iraqis as a more neutral party and Thursday's comments reflected a stark warning by the world body.

The U.N. report, which covers the period from April 1 to June 30, also warned that increasing reliance on heavily armed teams risks eroding the distinction between civilians and combatants and noted several reports of "killings carried out by privately hired contractors with security-related functions in support of U.S. government authorities."

In one recent case, guards working for the Australian-owned security company Unity Resources Group — whose employers are contracted by USAID — fired on a car as it approached their convoy on Tuesday, killing two women civilians before speeding away. The company said its guards feared a suicide attack and fired only after issuing several warnings for the car to stop.

In another high-profile case, Blackwater USA — the largest American firm working for the State Department in Iraq — is under scrutiny for the killing of 17 Iraqis after its guards opened fire on an intersection in central Baghdad on Sept. 16. The company also said its guards were responding to an armed attack.

Vuco said international humanitarian rights law applies equally to contractors who work for the mostly Western firms providing security to diplomats and aid groups as it does to other parties in a conflict.

"We will be stressing that in our communications with U.S. authorities. This includes the responsibility to investigate to supervise and prosecute those accused of wrongdoing," she said at a news conference in Baghdad.

"There cannot be rogue elements that are above the law. Definitely, we will be driving that point home time and again," Arikat said.

The UNAMI report also expressed concern that too many Iraqi civilians are being killed in U.S. military operations as part of a security crackdown in Baghdad and surrounding areas.

U.S. airstrikes reportedly killed at least 88 Iraqi civilians and many more died in raids by American ground forces during a military crackdown in Baghdad and surrounding areas, according to the 36-page report.

But the contractor shooting cases have provoked outrage among Iraqis who have long hated what they see as overly aggressive behavior by the security contractors. The Iraqi government has launched investigations and a joint U.S.-Iraqi panel has been created to review the practices of the security companies, which generally have enjoyed immunity and little oversight in Iraq.

UNAMI called on the U.S. government to establish mechanisms to hold security contractors accountable for unjustified killings and to ensure that offenses committed in Iraq "by all categories of U.S. contractor employees" are subject to prosecution under the law.

An order issued by the U.S.-led Coalition Provisional Authority in 2004 before the Iraqi government gained sovereignty gives American security companies immunity from Iraqi prosecution on issues arising from their contracts.

The U.N. said the order "enables the U.S. government to waive a contractor's immunity" but "to UNAMI'S knowledge it has not done so to date."

An Iraqi investigation into the Blackwater shooting found the guards opened fire without provocation and recommended that the State Department sever all contracts for the company's operations in Iraq within six months.

The United States has not made conclusive findings about the shooting, though there are multiple investigations under way and Congress has opened inquiries into the role of private security contractors.

The U.N. report also said Iraqi civilians continued to bear the brunt of ongoing violence by Sunni and Shiite militant groups, although it was again unable to provide casualty figures, saying it could not persuade the Iraqi government to release data compiled by the Health Ministry and other institutions.

"We again call upon the Iraqi government to release the figures, for the good of Iraq, for the good of Iraqi people," Arikat said.