Freshly leaked documents suggest that the civilian death toll during the Iraqi war has been underestimated, with sectarian violence being the major culprit in the widespread devastation.

The leaked reports, part of a huge cache of secret archives released Friday by WikiLeaks, begin to sketch out the specifics of exactly how many Iraqis died during the years-long conflict; more specifically, the documents unearth new and graphic details about how civilians perished.

According to the reports, it appears that most Iraqis died at the hands of their fellow countrymen -- a disturbing but not unexpected contention which reveals the sectarian nature of the conflict.

Other key elements in the leaked documents suggest that U.S. forces didn't adequately investigate cases of prisoner abuse by Iraqi police and military personnel, despite strong evidence of torture and mistreatment. Such contentions could place U.S. officials in violation of international law.

The Pentagon and U.S. military officials have strongly condemned WikiLeaks' release, saying that strategic U.S. military operations could be threatened.

"We deplore WikiLeaks for inducing individuals to break the law, leak classified documents and then cavalierly share that secret information with the world," Pentagon press secretary Geoff Morrell said Friday evening.

The documents date from Jan. 1, 2010 back to the beginning of 2004, and appear to have been filed by low-ranking officers. This is the second such release by WikiLeaks.

Despite the strongly-worded response, the Pentagon has downplayed many of the revelations in the reports as existing knowledge.

Still, war historian Sunil Ram pointed to the statistics and reports about civilian casualties as a significant trove of information.

"I think the critical one is the rise in about 15,000 to 20,000 Iraqi casualties," he told CTV News Channel Friday evening.

Ram based that number on previous reports from the group Iraq Body Count, who used press reports of killings as their main reporting tool.

These stats, along with the context surrounding the nature of the deaths, show that "this was not an insurgency, this was a civil war," Ram said.

He noted that Washington has gone to great pains to downplay the civilian casualties during the conflict in an attempt to sell the military effort as a "clean war." However, Ram said the numbers speak for themselves.

Equally troubling for the U.S. are other unsealed reports, which document instances in which Iraqi civilians died at the hands of American soldiers. Many instances occurred at checkpoints and during military operations.

In particular, at least four fatal cases involving U.S. helicopters and civilians have been unearthed.

Among the most violent was an incident on July 16, 2007 where 26 Iraqis were gunned down by a helicopter.

It's believed half of these casualties were civilians; still, the death toll may have been doubled since the incident was reported twice.

Earlier in 2007, an Apache chopper shot and killed two Iraqis who had reportedly been firing mortars. The men were shot despite making motions to surrender, the report states. Rules of engagement in such cases doesn't appear to be clear.

The bloodiest month in Iraq for civilians was December 2006, when 3,800 died during conflicts in Baghdad and elsewhere.

Meanwhile, U.K. newspaper the Guardian published an article about an incident where a prisoner was shot in the leg and then beaten in custody. The detainee, who was hit repeatedly with a large rod, suffered cracked ribs and several lacerations.

Despite evidence of the severe beating, U.S. officials ignored the case and did not investigate the actions of Iraqis security forces, the paper reported.

Similar controversies have played out in Canada following allegations that Canadian soldiers knowingly handed over Afghan detainees to local authorities, who then tortured their prisoners.

At best, critics have said that such reports undermine the legitimacy of the NATO campaign; at worse, such torture reports distill sentiment against NATO and create support for insurgents.