The affected companies have been notified of the decision, he said.

President Rafael Correa, a left-wing economist, has announced several times a plan to review and renegotiate 4,112 mining concessions that cover 2.8 million hectares in the country.

The latest measure affects two projects run by Canada's Ascendant Cooper Corp. Golden 1 and Golden 2, in the Junin project.

The company will keep the Magdalena concession in the Junin project, and the Chaucha project in Azuay province, which includes six concessions.

The government declared the concessions void because the companies that held them didn't comply with conditions that were set out when the concessions were awarded, Chiriboga said.

Chiriboga said that companies affected by this decision didn't pay or paid late payments, worth $1 to $16 per hectare, that would have allowed them to retain the properties.