Zimbabwe's government has said that it has taken majority ownership of foreign-owned mining firms which had not already given a controlling stake to black Zimbabweans.
Indigenisation Minister Saviour Kasukuwere said all such firms that did not meet a late 2011 deadline were now deemed to be in 51% state control.
He did not say which or how many firms would be affected.
Analysts have expressed scepticism and say it is a political move.
Some have said Mr Mugabe's regime was posturing ahead of elections he wants to hold later this year.
Mr Mugabe's coalition partner and long-time rival, Prime Minister Morgan Tsvangirai, has always opposed his plans to seize control of foreign firms.
Nic Borain, an independent political analyst based in South Africa, said: "I would treat this with quite a degree of scepticism.
"I would want to wait to see the specifics of how those shares would be transferred, how the assets would come to be in government hands, how government would exercise any control over those assets."
Mr Kasukuwere had previously said that most foreign miners were complying with the order to transfer majority ownership.
A number of foreign-owned mining companies have operations in Zimbabwe, including Rio Tinto and Anglo American.
Both firms have been unavailable for comment.
Mr Mugabe says such moves are need to right the wrongs of the colonial era, which left most of the economy in the hands of the white minority.
But his seizure of most of the country's white-owned land has been widely blamed for causing the country's economic collapse.