The carcasses of 87 elephants, killed and stripped of their tusks by poachers, have been discovered near a wildlife sanctuary in Botswana, a charity says.

The “fresh and recent” remains were discovered close to the protected Okavango Delta wildlife sanctuary by the Elephants Without Borders, which conducted an aerial survey for the Botswana government.

The conservation charity said the “alarming rate” of poaching deaths was the biggest seen anywhere in Africa.

But the government branded the figures "false and misleading", insisting Elephants Without Borders reported finding 53 carcasses, not 87.

"Of the aforementioned 53 reported, a verification mission between July and August established that the majority were not poached but rather died from natural causes and retaliatory killings as a result of human and wildlife conflicts," it said in a statement.

Survival International, a charity dedicated to tribal peoples, also expressed scepticism about the figures, claiming there is a "clamour" for rearming Botswanan wildlife guards, some of whom the charity has accused of "abuses against local people" and "extrajudicial killings".

Botswana has an estimated 130,000 elephants, the most of any country in Africa and was long viewed as a rare refuge for the creatures.

But the southern country is coming under increasing threat from poachers, who are increasingly killing elephants in the southern African country after wiping out large numbers in nearby Zambia and Angola, Elephants Without Borders said.

A similar census in 2014 found just nine carcasses, according to Mike Chase, the charity’s group director. The reported increase in elephant poaching in Botswana could reflect a trend in which poachers move into new territories as conditions become more difficult in regions where they usually operate.

Those conditions could include a dearth of elephants to kill after widespread poaching, or crackdowns on trafficking syndicates in some cases.

Tanzania's Selous region, for example, was heavily hit by elephant poachers but recent data indicates that the killing has slowed. Even so, killings intensified around the same time in Mozambique's Niassa reserve to the south, which is linked to the Selous by a wildlife corridor.

Elephants exported illegally from Laos to China for the tourist industry

The fight against elephant poaching has made some gains, including a ban on the ivory trade in China, the world's biggest consumer. But experts say the rate of annual elephant losses still exceeds the birth rate, and the encroachment of human settlements is reducing the animals' range.

Botswana, with a population of just over 2 million people, suffers some human-wildlife conflict but has more space than many other countries for animals to roam. Kenya, for example, has a population 25 times larger and is almost as big as Botswana in geographical size.

Botswana's security forces have also had a reputation — and faced criticism from neighbouring countries — for allegedly being quick to open fire on suspected poachers, including Namibians and Zimbabweans who were killed after illegally crossing the border.

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President Mokgweetsi Masisi, who took office in Botswana this year, has taken steps to reduce the use of military weapons in operations against poachers.

While the move may have alleviated tension with Botswana's neighbours, conservationists believe it could be providing an opening to emboldened ivory traffickers.

The government denied disarming poachers had had an impact on poaching. "The withdrawal of weapons from [the Department of Wildlife and National Parks] has not created any vacuum in anti-poaching operations as the anti-poaching unit in DWNP continues to play a pivotal role in combating wildlife crime through other strategic interventions," it said.

Poachers have targeted old bull elephants that presumably have the heaviest tusks, killing them when they go to drink at seasonal water sources, Mr Chase said.

"A clear order has been put out for tusks of a specific weight, and I suspect such large ivory is in heavy demand, considering that there are few large tuskers left in Africa," he added.