Poachers killed at least 86 elephants in Chad last week, including 33 pregnant females and 15 calves, conservation groups said Tuesday, warning that elephants in Central Africa risked being wiped out by such slaughters. The killing was the worst in the region since more than 300 elephants were slaughtered in Cameroon early last year. Both raids took place during the dry season, when poachers armed with automatic weapons carry out coordinated attacks on herds of elephants in the region. The attack was reported to have taken place on March 14 and 15 in southern Chad, near the border with Cameroon. Citing local officials, the World Wildlife Fund said the poachers were on horseback and spoke Arabic, suggesting that they may have been the same group involved in the 2012 attack in northern Cameroon. Conservationists warn that criminal gangs are trafficking huge quantities of tusks to cash in on soaring demand for ivory in Asia.