A farmer in South Africa has been killed by his pet hippopotamus - despite repeated warnings that it was a wild animal that could never be tamed.

Marius Els, 40, an army major, was bitten to death by the 1.2-tonne hippo he christened Humphrey and tried to domesticate on a farm in Free State province on Saturday.

Major Els's savaged body was found submerged in the river where, years earlier, the hippo had been rescued from a flood.

He grew too big for the people who adopted him and was bought by Major Els at the age of five months, becoming a pet on his 160-hectare farm and learning to swim with humans.

This year, Major Els was photographed riding on the five-year-old hippo's back.