Poachers have killed more than 600 rhinos in South Africa so far this year, figures showed Thursday, with losses close to the total number of animals slaughtered in 2012.

South Africa is home to the world's biggest rhino population but killings have surged in recent years to reach 668 animals last year from just 13 reported incidents in 2007.

"The total number of rhino poached since the beginning of the year has increased to 618," said the department of environmental affairs.

More than half were killed in the giant Kruger National Park which borders Mozambique in the east.

The bloodbath is fuelled by black market demand in Asia where consumers falsely believe the horns, the same composition as fingernails, have powerful healing properties.

A total of 191 suspected poachers have been arrested this year, with 24 in the past two weeks.