After a tense debate, the Convention on International Trade in Endangered Species (CITES), meeting in Doha, voted down Tanzania's request to sell 80.5 tonnes of stockpiled ivory to Japan and China.

Zambia later withdrew its own bid for a one-off sale of 21.7 tonnes worth several million US dollars.

Efforts by both countries to downlist wild populations of the intelligent mammals to a lower level of protection were also slapped down in separate votes.

"We are sitting on a treasure that we are not allowed to use to help our population, to help the poor build schools and roads," said Stanslaus Komba, from Tanzania's ministry of natural resources.

The move to reopen ivory trade -- banned since 1989 with the exception of a few one-time sales -- comes on the heels of a dramatic surge in illegal trafficking since 2005.

"Large-scale ivory seizures are becoming not only more frequent but larger in size," said Tom Milliken, head of the Elephant Trade Information System.

Organised crime syndicates in Asia have also gotten into the act to satisfy growing demand in the region, he said.

In Africa, the countries most directly involved in the traffic have been Nigeria and the Democratic Republic of Congo, while in Asia activity was particularly high in Thailand, he added.

Some 25 tonnes of the precious material -- culled from an estimated 2,600 elephants -- were confiscated last year, mainly in Asia, according to wildlife trade monitoring group TRAFFIC.

All told, tens of thousands of elephants are likely butchered every year for their tusks, experts say.

Poachers have taken to using heavy arms to carry out military-style operations, leaving local law enforcement outmatched.

"They fire on herds with rocket launchers," said Cosma Wilungula Balongelwa, a delegate from the Democratic Republic of Congo, citing cases from earlier this year.

Except for populations in four southern African nations, African elephants in two dozen other range states are listed on CITES Appendix I, which bans cross-border trade.

Tanzania and Zambia sought a downlisting to the less restrictive Appendix II, which allows commerce if it is monitored and deemed sustainable.

The one-off sales would have netted about 13 million US dollars (9.5 million euros), said TRAFFIC.

The last such sale in 2008 by Botswana, Namibia, South Africa and Zimbabwe set the clock running on a nine-year moratorium on international ivory sales, agreed upon at the last CITES meeting in 2007.

The recent surge in seizures has caused officials to question whether one-off sales stimulate illegal trade rather than stem it, as was once thought.

"In the last three years, the population of the Selous game reserve in Tanzania has declined by 30,000 elephants," Sam Wasser, director of the University of Washington's Center for Conservation Biology, said in an interview.

"Tanzania argues that they have just moved, but where did they go?" added Wasserman, whose laboratory has pieced together a genetic map of African elephants based on DNA take from dung samples that will allow police to trace seized ivory to its origin.

Conservation and wildlife groups applauded the decisions.

"Governments made the right move by rejecting the proposals," said the WWF's head of species programme, Carlos Drews.

"It is not the right time to be approving ivory sales due to increased elephant poaching in central and western Africa."

Both Tanzanian bids fell far short of the two-thirds majority needed to pass.

But Zambia -- whose bid was backed by China and Japan -- missed the downlisting by only a handful of votes, and said it may resubmit the measure in the finally plenary session on Thursday, permitted under CITES rules.

A separate proposal backed by 23 other elephant range nations that would have extended the trade moratorium on ivory trade to 20 years was withdrawn at the last minute.