“We have not received much (money) from the diamond industry at all,” Mugabe said in a two-hour interview screened late Thursday by state broadcaster Zimbabwe Broadcasting Corporation.
“Our people… have not been able to see or hear what was going on and lots of swindling, smuggling have taken place and the companies that have been mining virtually robbed us of our wealth.
“We have decided that this area should be a monopoly area and only the state should be able to do mining.”
Mines Minister Walter Chidhakwa last month announced the government had seized diamond mines in the eastern Chiadzwa district after their licences expired.
Zimbabwe last year ordered diamond mines, including joint ventures with Chinese companies mining in the Marange district, to join a government conglomerate.
The country’s diamond industry has been tainted by allegations of rights abuses including the killing and torture of workers.
Reports of abuse led to an international ban of gem exports from Marange between 2009 and 2011.
Diamonds were discovered in Marange in 2006, drawing thousands of small-time miners hoping to make a quick fortune.
The army cleared the area in late 2008, when rights groups said more than 200 people were killed.
The government in Harare pinned its hopes on the diamond industry to shore up the moribund economy, but with little success.
Zimbabwe, which earns most of its foreign exchange through mining, saw diamond production fall to 420,000 carats in the first five months of 2015 from 660,000 carats a year earlier, according to Bloomberg News.
Additional reporting: Sydney Morweng
