Lobby group Human Rights Watch has accused Zimbabwe's army of using forced labour, including children, to mine diamonds in the east of the country.

Local villagers who do not co-operate with the military are beaten and tortured, the US-based group says.

But in reality it was a systematic attempt to enable key army units, whose support President Mugabe needed following June's elections, to have access to riches, Human Rights Watch says.

If the diamond industry was legally regulated, Human Rights Watch estimates it could amount to $200m a month for the country.

It is calling for diamond exports from Zimbabwe to be banned and for the country to be suspended from the Kimberly Process - the certification scheme for diamonds - until the demilitarisation of the mines is achieved.

On Wednesday, Global Witness reported that the Kimberly process was failing - partly because of the situation in Zimbabwe.

Blood diamond scheme 'is failing'