Poachers have massacred 89 elephants in one night near the town of Ganba in southern Chad, conservation groups say.
The World Wildlife Fund (WWF) said in a written statement on Tuesday that about 50 Arabic-speaking poachers on horseback carried out the mass killing of the elephants last week.
The elephants killed last Thursday night, included 33 pregnant females and 15 calves, the WWF and the International Fund for Animal Welfare (IFAW) said, citing local officials.
The IFAW said the elephants' tusks had been removed.
The governments of Cameroon, the Central African Republic and Chad will meet in Yaounde this week to develop a regional anti-poaching strategy after conservationists said that elephants in Central Africa risked being wiped out by such slaughters.
Bas Huijbregts, head of WWF's campaign against illegal wildlife trade in the region, said the Chadian army was sent to stop the poachers.
"This tragedy shows once again the existential threat faced by Central Africa's elephants," Huijbregts said.
"In all likelihood this is the same group of Sudanese poachers who killed over 300 elephants in northern Cameroon in February 2012, forcing the country to mobilise its special forces to protect the region's remaining elephants."
Asian demand soars
Conservationists say that organised criminal gangs are illegally trafficking huge quantities of tusks to cash in on soaring demand for ivory in Asia.
WWF officials reported this month the discovery of 23 elephant carcasses in a Cameroon national park which had been stripped of their tusks.
"We urge governments to start putting in place this plan as early as next week, to safeguard the region's last elephants and rid it of this poaching threat once and for all," Huijbregts said.
"At its root, though, it is ending demand for ivory in countries like Thailand and China which will ensure the survival of Central Africa's elephants."
The price of ivory has passed $2,000 per kilogramme on the Asian black market, according to several non-government organisations.
Kelvin Alie, director of IFAW's Wildlife Crime and Consumer Awareness Programme, said that cross-border cooperation and intelligence-led enforcement were the only ways to bring ivory traffickers to justice.
"It is too big a problem for any one country to tackle," Alie said.
"We need range states, transit countries, and destination countries to share their law enforcement resources, including intelligence, or we'll never be in a position to shut down the kingpins of the international ivory trade."