An American investigator into the illegal ivory and rhino horn trade has been found stabbed to death in his home, Kenyan police said.

Esmond Bradley Martin was found at his home in Nairobi with a stab wound to the neck after a family member went to check on him after he did not respond to phone calls, according to Nicolas Kamwende, head of criminal investigations in the Kenyan capital.

Conservationist Paula Kahumbu said Mr Martin led investigations into the illegal trade of elephant ivory and rhino horn that threatens the two species with extinction.

Ms Kahumbu said he was at the forefront of exposing ivory traffickers in the US, Congo, Vietnam, Nigeria, Angola, China and recently Burma.