The Democratic Republic of Congo is to cancel "many" mining contracts and renegotiate others, a minister says.

The government said it wanted to ensure that the country`s vast mineral wealth was used to benefit its people.

Many Congolese suspect that mining deals are often corrupt and campaign group Global Witness says the review was hit by a lack of transparency.

DR Congo has huge reserves of gold, diamonds, copper and coltan, used in mobile phones.

Correspondents say these riches have been a key factor in the civil wars, instability and bad government the country has known since independence.

At least 60 contracts were cancelled last year and a commission was set up to review them.

DR Congo`s Deputy Mines Minister Victor Kasongo said it was clear "that none of the contracts met international standards".

"Many of them need to be re-negotiated and some of them have to be terminated, because when you do business every partner must be remunerated proportionate to their input," he told the BBC`s Focus on Africa programme.

"The state assets were undervalued, making our contribution seem smaller. In essence we are contributing too much. This creates some unfairness."

The mines review commission also recommended the cancellation of some contracts which it said had been awarded illegally in rebel-held areas in the east of the country.

The enquiry into the mining deals has not been made public, sparking condemnation by Global Witness.

The campaign group said a government task force had been set up to start renegotiating the contracts.

"We`re calling on the government to make sure this process of re-negotiation is transparent and open," Global Witnesses` Carina Tertsakian told the BBC.

"The task force is composed entirely of government ministers and we`re worried about what this might mean in terms of a lack of independence."

President Joseph Kabila won the country`s first democratic elections in 40 years in 2006.

His critics accuse him of agreeing deals with foreign mining companies which do not benefit local people.

Professor Peter Rosenblum from the US-based Carter Center, a consultant to the commission, said mining deals lie at the heart of DR Congo`s problems.

"The tragedy of the many tragedies in the Congo was that the people woke up after years of war and found that the family wealth had been given away, or sold off, or at least as far as people knew, it seemed to have just flitted away."