The world's largest saltwater crocodile in captivity has died in the Philippines, 17 months after the suspected man-eater was hunted down and put on display for tourists, his caretakers said Monday.

"Lolong", who measured 6.17 metres (20.24 feet), died on Sunday night from a mystery illness inside his small enclosure in Bunawan, a backwater town in the country's remote south.

"This is a very, very sad day for us. He had brought fame to our town. We are now thinking of having his remains preserved," town spokeswoman Welinda Elorde told AFP.

A government-sanctioned hunting party caught Lolong in a sprawling marsh close to Bunawan in September 2011 after it was suspected of biting the head off a young school girl and of eating a fisherman.

Its capture made the town famous and Lolong, named after a local crocodile hunter, became a big tourist attraction.

But it also put the spotlight on the plight of the crocodiles in the Philippines' remote marshes and rivers, as human habitation increasingly put them in conflict with the animals.

Animal rights groups also demanded Lolong be released back into the wild, arguing that the pen that held him was too small and stressful for an animal used to roaming great distances.

But Elorde said caretakers tried to give Lolong everything he needed in captivity, and that releasing him would have left him in the mercy of villagers who would hunt and kill him.

"We tried to give him the best place we could," she said.

The Philippine Star newspaper reported Monday that Lolong had been ailing since swallowing a cord three weeks ago, a claim Elorde denied.

"We have been alternately feeding him with meat and poultry, and there was no way he could have eaten anything other than that," she said.

The Guinness Book of World Records last year officially declared Lolong the largest crocodile of its kind in captivity.

It dislodged Cassius, a 5.48-metre crocodile kept in a park on an island off Australia's Queensland as the previous record holder.

Lolong belonged to the species Crocodylus Porosus, or the Indo-Pacific crocodile, the world's largest reptile, which experts say can live up to a century.

While not on the brink of extinction globally, it is critically endangered in the Philippines, where it is hunted for its hide.