TRAFFIC, a conservation group which tracks trends in wildlife trading, said there have been at least 13 large-scale seizures of over 800 kg (2,000 pounds) of ivory in 2011, more than double the 6 recorded in 2010.

"A conservative estimate of the weight of ivory seized in the 13 largest seizures in 2011 puts the figure at more than 23 totonesnnes, a figure that probably represents some 2,500 elephants, possibly more," it said in a statement.

Zimbabwe-based Tom Milliken, who manages TRAFFIC's Elephant Trade Information System, said it was the worst year for large seizures he had seen in the over two decades he has been running the database.

He said the poaching and illegal trade were consequences of China's investment drive into Africa to secure the mineral and energy resources it needs to fuel its economic growth.

"We've reached a point in Africa's history where there are more Asian nationals on the continent than ever before. They have contacts with the end use market and now they are at the source in Africa," he told Reuters.

"This is all adding up to an unprecedented assault on elephants and other wildlife," he said.

Milliken said some of the ivory that was making its way to illicit markets may be coming from African government stockpiles from previous seizures but the trade numbers and data from other wildlife monitors pointed to a rise in elephant killings.

"The trade data suggest that thousands of elephants are being killed a year ... I think central Africa has been brutally affected, especially Democratic Republic of Congo (DRC)," he said.

Milliken said elephant poaching was also taking place in Zimbabwe, Zambia, northern Mozambique, Tanzania and Kenya.

A global ban that was placed on the ivory trade in 1989 was widely credited with stemming a relentless slaughter of African elephants in countries such as Kenya. Occasional auctions from African government stockpiles have since been sanctioned.

Most of the illegal African ivory winds up in China or Thailand, according to TRAFFIC. Ivory is used in the making of jewelry and art carvings.

Estimates of Africa's elephant population vary widely from around 400,000 to 700,000.

In some southern African states such as Botswana there are large and growing populations and in South Africa there are concerns that elephant numbers have swelled to the point that they are damaging the environment in enclosed reserves.

But elsewhere the situation is far more bleak. In lawless regions of the DRC poaching is rampant.

(Editing by Giles Elgood)

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