Human rights groups have made similar accusations, but the charges carry particular weight coming from Kimberley Process investigators who visited Zimbabwe in June and July. Their recommendations are in a confidential report obtained by The Associated Press on Wednesday.
Zimbabwean authorities have repeatedly denied such charges, including in statements to Kimberley Process investigators and officials. The investigators said they found evidence contradicting the official account, and that information provided by Zimbabwean authorities "was false, and likely intentionally so".
The report was presented to Kimberley Process Certification Scheme officials, who were expected to decide this week on what to do about the southern African country. Their investigators recommended that Zimbabwe either be suspended or voluntarily suspend itself until it has met minimum standards for remaining part of the process.
The Kimberley Process was established in 2002 in an attempt to stem the flow of "blood diamonds" - gems sold to fund fighting across Africa. Participants must certify the origins of the diamonds being traded. Suspension could result in buyers shunning Zimbabwe's diamonds.
While the rough gems flowing from Zimbabwe's Marange field do not fit the strict Kimberley definition of conflict diamonds, the investigators said the lawlessness in the area would make it easy for traffickers to bring in such gems from other countries and then export them as Zimbabwean.
"Lawlessness, particularly when combined with violence and largely overseen by government entities, should not be the hallmark of any system deemed to be compliant" with the Kimberley process, the investigators added.
The investigators interviewed witnesses, victims and survivors of victims.
While illegal miners often fled when team members approached, seven told of working for soldiers who allowed them to keep only 10 percent of the proceeds of any diamonds recovered.
"Each one of these illegal miners reported seeing people killed and the numbers they cited ranged from one to seven," the report said. "This group also told members of the team that they observed extreme violence against illegal miners" by soldiers using rifles, dogs, batons and teargas.
The report said women "reported that, while under the custody of the security forces, they were raped repeatedly by military officers and that they have been forced to engage in sex with illegal miners. One victim told the team that she tested HIV-positive after she had been forced to have sex with two men and then raped by a military officer".
The investigators said it was "credible" that syndicates operated by police and soldiers have been smuggling rough diamonds out of Marange since at least 2008, and likely since formal production began in 2007.
"The team concludes that the government of Zimbabwe authorities are aware of these syndicates and ongoing smuggling operations and have permitted them to continue," the report said.
London-based Global Witness, a human rights groups that tracks how Africa's mineral wealth is misused, has complained that the Kimberley Process has so far failed to address smuggling, money laundering and human rights abuses in Marange.
Human Rights Watch called last week for Zimbabwe to be suspended from the Kimberley Process. The international rights watchdog has said repeatedly that Zimbabwean soldiers are smuggling diamonds and killing and beating civilians to consolidate a hold on Marange that benefits the Zanu-PF party of long-time President Robert Mugabe.
Mugabe entered into a coalition with his rival Morgan Tsvangirai in February, but Tsvangirai this month suspended his participation, accusing Mugabe of continuing human rights abuses and undermining the unity agreement.According to Kimberley process officials, Zimbabwe exported nearly 800 000 carats of diamonds from three fields, including Marange, last year. Zimbabwe has no diamond processing facilities, so exports only rough gems. - Sapa-AP
