PRETORIA, South Africa — Poachers have killed a record 688 rhinos in South Africa so far this year, more than the entire number slaughtered in 2012, according to figures issued Sunday, World Rhino Day.

South Africa is home to the world's biggest rhinoceros population but killings have surged in recent years to feed black market demand in Asia for their horns, from just 13 reported incidents in 2007.

South Africa's renowned Kruger park, which borders Mozambique, suffered the largest number of killings, with 425 rhinos killed since January, according to the environment ministry figures.

WWF's rhino coordinator Joe Shaw warned recently that the situation was becoming even more critical, with the number of rhinos killed set to exceed births, leading to an overall population decline.

Asian consumers falsely believe the horns, the same material as fingernails, have powerful healing properties.

South Africa is home to around 80 percent of the world's rhino population, estimated at more than 25,000.

A total of 668 were killed in South Africa last year.