Soaring commodity prices and acquisitions helped mining group Xstrata, the world's fourth-largest copper producer, double its net income in 2006.

Copper prices surged by more than 80% last year, boosted by demand from rapidly expanding economies such as China, the company said. Zinc prices more than doubled during the same period.

"Commodity prices have again performed very strongly in 2006," Xstrata said in a statement to the London Stock Exchange.

"While it is unlikely that average prices for base metals will continue to rise at a similar rate in 2007, the fundamental outlook for the industry remains positive."

Xstrata is Swiss-based but its shares are listed in London and is 36%-owned by commodities group Glencore.

The company also said it was benefiting from three big acquisitions it made in 2006, and that it would continue to look for deals as it rapidly pays off its debt.

However, it would not comment on press speculation that it could get involved in a possible break-up of bigger South African rival Anglo American.

"We are alive to M&A (merger and acquisition) opportunities all the time," chief executive Mick Davis said.

Xstrata made three big acquisitions in 2006 - one third of Colombia's Cerrejon coal operation, Peru's Tintaya copper mine and, the biggest, Canadian miner Falconbridge.

The company won control of Falconbridge after a heated battle against Inco and copper miner Phelps Dodge.

The $18.8bn (about £9bn) deal allowed Xstrata to diversify into nickel and aluminum and enter the North American market.

Including results from Falconbridge as if it was a part of the company all year, Xstrata said that net income more than doubled to $4.89bn in the 12 months through December 31, from $2.23bn in the previous year.

Analysts had forecast adjusted profit of $4.6bn.

Sales including what Falconbridge would have contributed rose 56% to $26.9bn. Xstrata did not give results without Falconbridge.

Deutsche Bank analysts praised Xstrata's performance. "Overall a solid result, highlighting the potential for strong earnings growth in 2007," they wrote in a note.

Shares in Xstrata rose 70p to £24 in yesterday's London dealing.

From a small Swiss-domiciled producer of steel alloys known as Sudelektra Holding in the late 1990s, Xstrata has grown rapidly to challenge the world's big three miners -- BHP Billiton, Rio Tinto and Anglo.

Its acquisition spree has left it with net debt of more than $13bn, but chief financial officer Trevor Reid said high metal prices meant the group would reduce that quickly and cut gearing - its ratio of debt to equity - to within its target range of 30% to 35% this year, from 41% at the end of 2006.

Some analysts think Xstrata should increase its presence in bulk commodities, which are based on negotiated prices, to cut its exposure to more volatile trading ex-change metals.

In other mining industry news, Mark Moody-Stuart, the chairman of Anglo American, said commodity prices would remain high in the near-term with no sign of a collapse in the US economy.