Criminal gangs and rebel militias hunt dwindling herds for tusks that fetch many thousands of dollars per kilo, the Convention on International Trade in Endangered Species said.
"Today we are confronting a situation of industrial-scale poaching and smuggling, the involvement of organized transnational criminal organizations, the involvement of rebel militia," CITES secretary-general John Scanlon told a briefing.
Fighters of the Lord's Resistance Army (LRA) were sanctioned by the Security Council this year for illegal hunting and ivory trade, particularly in central Africa, he said.
The 2013 estimated figure is less than the peak of 25,000 elephants poached in 2011. But it was the third straight year that more than 20,000 were killed illegally on the continent that has an estimated 500,000 elephants left, according to CITES which monitors 51 sites, including national parks.
"It (poaching) is leveling off, but at a level that is far too high. The number of elephants that are killed is far exceeding the number of elephants being born," Scanlon said.
Large seizures of smuggled ivory in Africa, those over 500 kilos, rose in 2013, for the first time exceeding those in Asia, according to CITES. Its 1975 pact to ban or restrict trade in endangered species has been ratified by 180 countries.
A record 40,000 kilos were confiscated last year, already exceeded by an estimated 55,000 kilos seized this year, it said.
This was due to better enforcement especially in Uganda, Tanzania and Kenya, which accounted for 80 percent of the large-scale seizures in Africa last year, Scanlon said.
"We need to deploy the same sort of techniques that are deployed to combat other serious crimes such as illicit trade in narcotics, human trafficking or illicit trade in arms," he said. Rangers, custom officials and prosecutors must tackle poaching, driven by speculators betting on extinction, he said.