Despite a 23-year ban on international trade in ivory, elephants continue to be shot for their prized tusks, with much of the material ending up on sale in China.

The very future of the African elephant, the largest land animal on Earth, could be at risk.

Last year saw the highest number of large seizures of illegal ivory for more than two decades.

From Kenya to Zambia, African law-enforcement and conservation authorities are facing a continuing battle with the poachers.

And it is in the Democratic Republic of Congo, where governance is at its weakest, that the elephant population is being hit hardest, with thousands of elephants killed each year.

Conservationists have recorded steep declines in population and fear fewer than 20,000 of the region's forest elephants remain in the Congo basin.

Find out more Panorama: Ivory Wars - Out Of Africa, is broadcast on BBC One, Thursday 12 April at 21:00 BST Or catch up later via iPlayer

In Kinshasa, the capital of DRC, poached ivory is openly on sale at large, unregulated markets.

While traders were wary of being filmed by a BBC TV crew, a Chinese undercover reporter working for Panorama quickly attracted the attention of sellers, using the Chinese word for ivory to good effect.

The reporter was offered whole raw ivory tusks in one market, including one giant piece about 1.5m long for $10,000 (£6,000).

Tom Milliken, who monitors and campaigns against the illegal trade in ivory, was not surprised at Panorama's findings. "These markets are patronised by ex-pat communities and Chinese business," he said.

The destinations of all contraband ivory are always neighbouring countries around China Julius Kipng'etich, Kenya Wildlife Service

"We've been in the market in Kinshasa where we've estimated the ivory from more than 200 elephants has been on the tables for sale on a single day," he said.

Poached ivory from Congo or other countries is often shipped out via Kenya. Despite policing efforts, nearly 85% of ivory seized from around the world that could be traced had come from or passed through East Africa, much of it via the international airport at Nairobi.

Tonnes of ivory

Kenyan officials are in no doubt of its destination. "Ninety per cent of all the people we have arrested at the airports ferrying ivory are Chinese," said Julius Kipng'etich, director of the Kenya Wildlife Service.

"The destinations of all contraband ivory are always neighbouring countries around China."

Until the middle of last year Malaysia had not made a single large ivory seizure in nearly a decade. But there have been several large seizures since then, amounting to six tonnes of ivory that would have come from approximately 700 dead elephants.

But Malaysia is just one of a number of staging posts for the ivory. Most is on its way to China where it has been traded and treasured for centuries and remains available legally because of an internationally sanctioned deal.

Image caption Several large ivory hauls have been made in Malaysia

A 1989 ban rules out international trade, but in 2008, China and Japan were allowed to make a one-off purchase of legally sourced African ivory, provided there was proper regulation of the domestic market.

Every ivory shop has to be officially registered with the authorities and every item on display is supposed to have its own identification card so that every piece of ivory can be tracked after sale.

But Panorama had no difficultly buying ivory without certification at one of the state-approved shops, licensed by the authorities to sell ivory, that exist in a number of Chinese cities.

At the Friendship Store in Guangzhou, a BBC undercover team found many items with no accompanying certificate on display.

The team bought a necklace clasp from the shop which cost around £15, but the shop did not issue an ID card with it, making it impossible to prove that the ivory was legal.

The findings are in line with other reports on ivory sales in China including by ivory trade expert Dr Esmond Bradley Martin. "What we found in Guangzhou was that 63% of the items did not have the proper identification."

"Now the regulations also say… you need to have it close-by to the individual piece. We found that that wasn't always the case."

According to the Friendship Store, all its ivory products complied with regulations, and they had all the necessary paperwork on the day we filmed.

Black market

The domestic market provides opportunity for people to launder illegally obtained ivory Grace Ge Gabriel, International Fund for Animal Welfare

Away from the legal shops, Panorama was also able to access ivory in China on the black market.

One dealer offered 15 items of ivory worth nearly £50,000, which she said could be delivered within 24 hours. The biggest single item she had on sale was an uncarved tusk, priced at £4,000.

No direct link has yet been found between the legal sales and increased killings or trade. But campaigners fear the existence of a legal trade is helping to provide cover for a much more extensive black market.

The decision to allow further legal ivory into the country in 2008 made the situation worse, according to Grace Ge Gabriel, from the International Fund for Animal Welfare.

"We have found that every one legal activity comes with nearly six illegal trading activities. So this domestic market provides opportunity for people to launder illegally obtained ivory," she said.

In a statement, the Chinese government said it had a "consistent and firm position to fight against the illegal trade of ivory". It said possible individual breaches should not be used to deny "the efforts and progress China has made".

Image caption Ivory has been prized in China for centuries

The debate over the legal ivory trade is set to be reignited later this year when more African countries are expected to put in requests to sell stockpiled ivory.

Supporters say countries that properly protect their elephants should be allowed to profit from them. "It's vital that local people and the countries where elephants are present in large numbers get a benefit, economic benefit from the use of ivory," said Robin Sharp, of the European Sustainable Use Specialist Group

But opponents argue further sales will fuel demand and fear that China's booming economy means there will be an ever-growing market. "What is at the heart of the illegal killing of elephants in Africa? Money," concludes Dr Bradley Martin.

Securing the future of Africa's elephant will mean not just beating the poachers but also tackling black-market sales on the other side of the world in China.

Panorama: Ivory Wars - Out Of Africa , is broadcast on BBC One, Thursday 12 April at 21:00 BST and then available online via iPlayer (UK only) at the above link.