Nepalese animal rights groups pleaded Monday for the life of a lovelorn elephant which has trampled several people to death and is being hunted down by an army execution squad.

The male tusker, named Dhrube by locals, has been targeting humans on a killing spree in southern Nepal after being kept from potential mates, experts say, and is suspected of killing up to 15 people over four years.

"Killing the love-struck elephant is unethical, illegal, inhumane and unnecessary," Animal Nepal and Animal Welfare Network Nepal (AWNN) said in a joint statement.

Rangers removed the beast's tusks after it was suspected of killing two people in separate incidents in November -- but they then attached a tracking device and set it free.

It is suspected of killing six people across a wide swathe of Nepal's southern plains since then, including a couple in their 60s, and the army launched a shoot-to-kill hunt last week in Chitwan National Park.

The elephant first came to the attention of authorities five years ago when it destroyed an army post in an attack on soldiers in Chitwan, 150 kilometres (95 miles) south of Kathmandu.

The tusker, named after the army post, is accused of killing a soldier in Chitwan soon afterwards.

Rangers suggest the animal went rogue after being prevented from mating with females in Chitwan.

"Elephants are naturally docile animals that do not attack humans unless provoked," said Pramada Shah of AWNN.

"The situation has been caused by human failure to manage the elephant correctly. It is therefore our responsibility to find a legal and humane solution."

The groups called for park authorities to "resocialise" Dhrube.

Nepal has about 300 elephants, including around 100 domesticated adults which take tourists on jungle rides.