Rhino poaching in South Africa has accelerated in the last year, despite a crackdown on enforcing the law.

In 2011, 448 rhinoceros were killed in poaching-related activity, according to official government statistics.

The annual total includes 19 endangered black rhinos, of which fewer than 5,000 remain in the wild.

In 2010, 333 South African rhinos were killed by poachers, nearly three times the number killed in 2009.

More than half of South Africa's rhino deaths occurred in Kruger National Park, the country's premier tourist destination, which is renowned for its variety of African wildlife.

The park lost a total of 252 rhinos to poaching in 2011, and authorities from South Africa National Parks said it was one of their "worst years" for rhino poaching across the country.

The new statistics come shortly after field rangers at Kruger National Park found eight carcasses with their horns missing. Five poachers were shot dead by park rangers in the early weeks of 2012.

South African law enforcement officers made 232 poaching-related arrests in 2011, compared to 165 the previous year. Sentences have increased in recent years, with poachers and horn smugglers receiving as long as 16 years in prison.

WWF's wildlife trade policy analyst Dr Colman O'Criodain said a record number of rhinos were poached in 2011. "If left unchecked, poaching gangs could put the survival of these iconic species in jeopardy," he warned.

Dr Morné du Plessis, CEO of WWF-South Africa, said rhino poaching was being carried out by sophisticated international crime syndicates that smuggle horns to Asia.

"It's not enough to bust the little guy; investigators need to shut down the kingpins organising these criminal operations. Governments in Africa and Asia must work together across borders to stop the illegal trade," he said.

A record number of ivory seizures was recorded for 2011, with the recent upsurge in rhino poaching pointing to an increased demand for rhino horn in Asia. Rhino horn has been used in traditional Chinese medicine to treat fevers whereas, in Vietnam, it is commonly prescribed by some medical practitioners as a "detoxicant" and claimed to be a cancer cure.

Rhino trade expert for wildlife monitoring organisation TRAFFIC, Tom Milliken, said rhino horn has also gained popularity among wealthy Vietnamese elites and business people to give as a gift, when currying political favour, or taking as an antidote to overindulgence. "But killing endangered rhinos to mitigate a hangover is a criminal way to see in the New Year."

The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) has found that consumer demand in Vietnam is driving much of the rhino poaching. CITES has also ruled that Vietnam needs to show progress in curtailing illegal trade in rhino parts and by-products.

"So far we have yet to see Vietnam respond to this ruling from CITES," says O'Criodain.

"CITES must put pressure on Vietnam to respond meaningfully, as it has done with other countries whose compliance with the convention has been called into question."

Because South Africa is home to most of the world's rhinos, the country has been at the centre of the poaching crisis. However, rhinos in other African and Asian countries are also being targeted by poachers.

WWF announced the extinction of rhinos in Vietnam in October 2011. The last Javan rhinoceros in the country was killed by poachers and its horn removed. However, in Nepal, strong conservation and law enforcement efforts ensured that no rhinos were lost to poaching in 2011.