A group of poachers last week massacred 89 elephants in one night near the town of Ganba in southern Chad, the World Wildlife Fund (WWF) said in a statement Tuesday.
Some 50 Arabic-speaking poachers on horseback carried out the mass killing of the elephants, including 33 pregnant females and 15 calves last Thursday night, the WWF said, citing local officials.
According to the organisation the Chadian army was sent to stop the poachers.
"This tragedy shows once again the existential threat faced by Central Africa's elephants," said Bas Huijbregts, head of WWF's campaign against illegal wildlife trade in the region.
"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."
Poachers in central Africa take advantage of vast unoccupied areas and porous borders to move from one country to another. The WWF believes ivory trafficking is used to finance various armed groups.
Between February 10 and March 1, WWF officials reported the discovery of 23 elephant carcasses in a Cameroon national park which had been stripped of their tusks.
The governments of Cameroon, the Central African Republic and Chad will meet in Yaounde this week to develop a regional anti-poaching strategy.
"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," he added.
The price of ivory has passed $2,000 (1,500 euro) on the Asian black market, according to several NGOs.