Johannesburg - Twenty years after the decimation of Africa's elephant population through poaching prompted a ban on the international ivory trade, animal rights activists are calling for a new all-out ban, saying partial sales have led to a fresh spike in poaching. Saturday marks the 20th anniversary of the Convention on International Trade in Endangered Species (CITES) ban on ivory trade.

The decision, taken on October 17th, 1989 in Lausanne, Switzerland, by the UN-backed CITES was in response to alarming levels of elephant poaching in Africa in the 1980s.

Africa's elephant population from about 1.2 million to 600,000 in the space of 10 years before the ban, according to the International Fund for Animal Welfare.

Following the ban, "ivory prices plummeted and so too did the incentives to kill elephants - a good example of a conservation plan," IFAW's Southern Africa director Jason Bell-Leask wrote in a opinion article in South Africa's Sunday Independent this month.

But as elephant populations began to recover, CITES, which has 171 members, also came under pressure to relax the ban to allow some African countries, which had well-managed, healthy elephant populations, sell off their stockpiles of the so-called white gold.

In 1999, CITES allowed the first such one-off sale. Botswana, Namibia and Zimbabwe were allowed sell 50 tonnes of ivory to Japan.

In 2007, CITES went further, allowing the same three countries plus South Africa to sell 106 tonnes of ivory that had accumulated in their national parks to Japan and China.

South Africa estimates the four countries together have over 312,000 elephants, or over half the continent's current estimated population of 470,000.

The ivory comes mostly from elephants that died a natural death, or, in the case of South Africa, elephants that were culled before a moratorium on culling in 1995. CITES ordered that the proceeds of the sale be put towards wildlife management and community development.

IFAW, Germany's Pro Wildlife and other animal rights group say these sales have whetted the demand for ivory in Asia, where ivory is used mainly in carved ornaments, and led to an increase in elephant poaching.

They point to large seizures of ivory by authorities across Africa and Asia over the past year as proof of a resurgent black-market trade, which they say is leading to the killing of over 30,000 elephants a year.

The relaxation of the ban had caused a "serious problem, which if not curtailed soon, will take us back to the 'killing fields' of the 1980s," Bell-Leask warned.

In March, authorities in Vietnam seized 6.3 tons of ivory originating from Tanzania, followed by another 2 tons, also coming from Tanzania, in August.

Between January and September, nearly 24 tons of ivory was confiscated worldwide, Pro Wildlife says, listing each seizure. In the meantime, black-market prices for raw ivory continue to rocket, exceeding 1,000 dollars a kilogramme, according to some reports.

As the CITES ban turns 20, Tanzania and Zambia have petitioned CITES to further open up the trade by allowing them to also sell off ivory stocks, according to Pro Wildlife. Mozambique is also preparing a similar submission, the German organization says.

At the same time, seven other African countries, which are battling to contain poaching - Kenya, Ghana, Liberia, Mali, Sierra Leone, Togo and Congo Brazzaville - are calling for a return to a complete ivory ban

CITES will decide on which route to take at its next conference, set to take place in March 2010 in Qatar. The four countries that liquidated their stocks have been banned from any further trade in ivory for nine years.