The world's biggest diversified mining group BHP Billiton has reported a 33% slump in profits during the December to February period.

The group reported a net profit of $406m (�278.6m; 450m euros) compared to $604m a year earlier.

Weak copper prices pushed earnings from its base metals division down by more than a half compared to the same period a year earlier.

The copper slump was only partially offset by higher silver output and the opening of a new zinc mine in Peru.

And the company expressed concern over the strength of the economic recovery, saying it had seen little evidence of an increase in demand.

"This situation will limit price increases for those commodities, at least in the short term, and will continue to impact on our earnings," said the group's deputy chief executive Brian Gilbertson.

The mining giant was created by last year's merger of Australia's BHP and London-based Billiton.