BAGHDAD — The U.N. has called on Iraq to conduct an independent investigation into the killings of 34 people at an Iranian opposition base after Iraqi authorities, who authorized a raid on the camp, suggested that the group might have executed its own members.

Wildly conflicting accounts of how the members of the People’s Mujahedeen Organization of Iran (PMOI) were killed have highlighted the dilemma over the last remaining stronghold of the group invited in by Saddam Hussein and disarmed by the United States.

In a statement issued late Saturday, the United Nations said it expected a commission of inquiry pledged by the Iraqi government to be independent. That commission, however, will include prime ministry and Iraqi military officials as well as a cross-section of political parties and is unlikely to meet that requirement, according to Iraqi government officials.

Iraqi government spokesman Ali Dubbagh said earlier this week that some of the dead were likely executed by camp leaders trying to prevent them from leaving.

Saad al-Muttalibi, an advisor to Prime Minister Nouri al-Maliki, said forensic tests, including some by U.S. experts, have been completed on the bodies to determine whether a medical team’s initial findings had been correct.

“”They were shot execution-style,”” al-Muttalibi told the Christian Science Monitor. “”The first medical reports indicated they were shot at very close range — gunpowder was found on the wounds.””

He also said they appear to be have been shot with handguns rather than the rifles used by the Iraqi military.

The U.N. earlier this week confirmed it had seen 28 bodies in a visit to the camp and knew of six others. It said dozens more had been injured in the operation before dawn on April 8, when Iraqi forces moved in to reclaim part of the huge base 70 miles north of Baghdad.

The U.N. said in the statement that it had repeatedly urged the Iraqi government to refrain from the use of force.