More than 1,000 rhinos were illegally killed in South Africa last year, an increase of 50% on the previous year, official figures have shown.
The South African Department of Environmental Affairs showed that 1,004 rhinos were poached in the country in 2013, up from 668 rhinos killed for their horn in 2012.
Top safari destination Kruger National Park, which borders Mozambique, bore the brunt of the poaching, with 606 rhino deaths.
Some 37 rhinos have already been killed this year, 34 of them killed in Kruger.
South African officials said the number of rhino poachers arrested during 2013 has also increased, with 343 being arrested, 133 of them in Kruger National Park, up from 267 alleged poachers arrested in 2012.
Six poachers have been arrested so far this year.
The increase in poaching brings South Africa's white rhino population ever closer to the "tipping point" where deaths will outnumber births and the population will go into serious decline, conservation experts warned.
The number of rhinos poached in South Africa has increased year on year in recent years to meet rising demand for rhino horn in China and particularly Vietnam, where it is used as a status symbol and health tonic for disease and even hangovers.
Experts warn there are links between criminal gangs responsible for smuggling the rhino horns out of Africa and to Asia and other forms of organised crime including people trafficking, drug smuggling and illegal arms trade.
Mozambique is a transit point for rhino smuggling activities and a base for poachers who cross the border to kill rhinos, wildlife trade monitoring network Traffic said.
Tom Milliken, Traffic's rhino expert, said: "South Africa and Mozambique must decisively up their game if they hope to stop this blatant robbery of South Africa's natural heritage.
"2014 must mark the turning point where the world, collectively, says 'enough is enough' and brings these criminal networks down.
"Rhino horn trafficking and consumption are not simply environmental issues, they represent threats to the very fabric of society."
Dr Jo Shaw, rhino programme manager for WWF-South Africa said: "These criminal networks are threatening our national security and damaging our economy by frightening away tourists."
She said agreements between South Africa and Vietnam and China on tackling wildlife trafficking had to translate into action on the ground.
And she said: "It would be encouraging to see more significant arrests higher up the trade chain, and to see current arrests resulting in convictions with strong sentences which will effectively deter this criminal activity.
"More significant action to root out corruption would also be welcome."