Wildlife officials in the West African nation of Mali say motorcycle-riding poachers have killed at least 19 elephants in the country since the start of the year.

Soumana Timbo, assistant director of the government's conservation efforts, on Wednesday described the extent of the elephant slaughter around the Malian town of Gourma.

It has been difficult for Malian wildlife officials to patrol the area because Gourma is located in the zone where Islamic extremists are still active.

It is believed there are between 350 and 700 elephants left in Mali, and they are under growing threat not only from humans but from climate change.