International diamond watchdog the Kimberley Process (KP) has certified Zimbabwe's Diamond Mining Company to sell gems from the violence-tainted Marange fields, state media reported on Sunday.
The firm, a joint venture between the Zimbabwean government and a company in the United Arab Emirates, became the fourth mine in the area to get the nod after monitors inspected its operations, said The Sunday Mail.
"The report confirms that we met all the requirements, from production to sort house," Prince Mupazviriho, permanent secretary in the mines ministry, told the newspaper.
"Systems we have built in terms of diamond mining are robust. Not only have we met KP standards, we have exceeded them."
The Kimberley Process, founded to stop the trade in so-called "blood diamonds", has come under fire from activists for being soft on abuses in Marange.
Human Rights Watch alleges that President Robert Mugabe's army killed more than 200 people two years after the 2006 discovery of the diamond fields in an operation to clear small-scale miners from the area.
The BBC reported last year on a camp run by Zimbabwean security forces where civilians were forced to dig for diamonds and tortured, claims the government called "ridiculous".
The United States in 2008 slapped sanctions on two firms mining in the eastern region, Marange Resources and Mbada, which are mining at the scene of alleged human rights abuses, while powerful US-based diamond trading group Rapaport has boycotted all Marange gems.
Of the five firms operating in Marange, just one has yet to receive Kimberley Process certification, Sino-Zimbabwe.
All the firms are jointly owned by the Zimbabwean government and foreign investors.
Zimbabwe says it expects to rake in $600m from diamond sales in 2012.