Johannesburg - Two Zimbabwean diamond companies operating in the controversial Marange fields have been added to the US list of sanctioned entities.
The Treasury's Office of Foreign Assets Control (OFAC) updated its specially designated nationals list to include the companies - Mbada Diamonds and Marange Resources.
Both companies operate their Marange mines in a joint venture with the Zimbabwe Mining Development Corporation, a state-owned company already on the OFAC list.
US citizens are prohibited from dealing with individuals or companies on the OFAC list.
The inclusion of the companies on the list comes just weeks after the Kimberley Process (KP) decided to allow Zimbabwe to export diamonds from the Marange region.
Many civic groups have criticised the KP's decision, saying the decision has made a farce of its certification scheme that aimed to curtail trade of blood diamonds.
Blood diamonds have fuelled civil wars in many African countries and the human rights abuses reported at Marange has earned the diamonds it yields the same status.
As recently as the end of August this year, Human Rights Watch reported that there were still "rampant abuses" taking place in the Marange diamond fields.
Zimbabwe's mines ministry has been tasked with leading the way for the country's economic recovery project, which envisions its mining sector contributing in excess of 50% of its gross domestic product.