Julius Kipng'etich said 2009 had been a bad year for rhino conservation
Kenyan authorities have arrested a gang suspected of killing a white rhino and cutting off and selling its horns.
Julius Kipng'etich of the Kenya Wildlife Service said the suspects were caught with two rhino horns and 647,000 shillings ($8,500; £5,300) in cash.
It is thought some of the 12 suspects were buyers of the horns and had used the money to pay the poachers.
Kenya had many thousands of rhinos in the 1970s but only hundreds remain after decades of poaching.
The hunters supply an illegal trade in rhino horns, which are widely used in traditional medicines in Asia.
Lobby groups warned last month that rhino poaching around the world was on the rise despite efforts to protect the animals.
A report funded by WWF International suggested that a decline in law enforcement is the main reason for the rise in poaching in Africa.
African rhino populations have been slashed in recent years
The report found that 95% of rhino poaching in the continent since 2006 had occurred in Zimbabwe and South Africa.
Mr Kipng'etich said Kenya had the world's third-largest rhino population with 610 black rhinos and 240 white ones.
But he said 2009 had been a bad year, with poachers killing 12 black rhinos and six white ones.
The gang of 12 men was arrested near a private ranch in Laikipia West in the Rift Valley Province after a man-hunt lasting several days.
The ranch's 10-year-old female white rhino was found dead on 28 December.