However, the report said poaching numbers had dropped slightly compared to the previous two years.
Transnational organised crime appeared to be involved in the trade, it added.
Cites, which is based in Geneva, is responsible for regulating the international trade in more than 35,000 species of plants and animals.
For the first time, more large-scale consignments of ivory have been seized in Africa rather than in Asia.
Conservationists say that even in some of the monitored elephant populations, poaching is actually increasing.
The Cites poaching estimates were based on data from 51 sites across Africa, which accounted for 30-40 percent of the continent's elephant population.
Figures from those sites were extended to estimate the total numbers killed in Africa