Two critically-endangered Sumatran elephants have been found dead in Indonesia's Tesso Nilo national park, with environmentalists accusing poachers of poisoning them.

“The blood is very dark, it was found in ice cavities below the belly and when we broke these cavities with a poll pick, the blood came running out,” Semyon Grigoriev, head of the Museum of Mammoths of the Institute of Applied Ecology of the North at the North Eastern Federal University, said.