Poachers killed nearly 450 elephants in Cameroon to take their ivory.
The mass killing reflects a trend where well-armed poachers with sophisticated weapons are decimating populations.
The UN watchdog into the illegal wildlife trade on Tuesday voiced "grave concern" at a spike in African elephant poaching after nearly 450 of the animals were killed in Cameroon.
The head of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), John Scanlon, pointed at recent reports of mass poaching for ivory in Cameroon's Bouba Ndjida National Park.
"This most recent incident of poaching elephants is on a massive scale," said Scanlon. "It reflects a new trend we are detecting across many range states, where well-armed poachers with sophisticated weapons decimate elephant populations, often with impunity."
CITES is offering African governments support to hunt down the criminals and to locate and seize the poached ivory. Potential transit and destination countries had been urged to remain extremely vigilant and to cooperate.
The CITES program on elephants revealed increasing levels of poaching in 2011.
"This spike in elephant poaching is of grave concern not only to Cameroon, a member state to CITES, but to all 38 range states of the African elephant," said Scanlon.
CITES said elephants have been slaughtered by groups from Chad and the Sudan in recent weeks, taking advantage of the dry season.
The poached ivory is believed to be traded for money, weapons and munition, fueling conflicts in neighboring countries.
The UN agency said it will contact the ministers responsible for forests and wildlife from Cameroon, Chad, the Central African Republic, the Democratic Republic of the Congo and Sudan to offer anti-poaching support.
Scanlon has designated Ben Janse Van Rensburg, a senior CITES security official with experience in fighting poaching, to coordinate support in response to the major elephant slaughters.
Van Rensburg is working with other international agencies including the International Consortium on Combating Wildlife Crime, Interpol, the World Customs Organization, the UN Office on Drugs and Crime and the World Bank.