A white tiger has attacked and killed a youth who apparently jumped into its enclosure at a zoo in the Indian capital.

Witnesses said the tiger grabbed the man by the neck as horrified onlookers at the National Zoological Park in New Delhi screamed and threw sticks and stones to try to save him.

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One witness said he raced to the enclosure after hearing screams to see the victim locked in the tiger’s jaws, “writhing badly in pain”.

“He kept suffering for the next 10-15 minutes, but nobody helped him,” Himanshu, who gave only one name, told the CNN-IBN news channel on Tuesday.

The head of the zoo told AFP a guard posted at the enclosure raised the alarm, but the victim was dead before anything could be done.

“We do have tranquillising guns but they are at the zoo hospital. By the time we could have organised those, he was killed,” zoo director Amitabh Agnihotri said.

A worker closes the gates at New Delhi Zoo. Photo: Getty

Witnesses had said the railings around the tiger enclosure were low and speculated the victim might have fallen in.

But Agnihotri defended the zoo. “There are guards there. If we increase the height of the fencing, how will people be able to look at the animal?” he said.

A statement from the zoo said the victim was about 20 years old, contradicting earlier reports he was a teenager.

One official said he also appeared to have been “under the influence of alcohol”.

“Security had tried to keep him away from the enclosure, but he somehow managed to jump in and the white tiger who was present at the enclosure leapt on to him,” junior official Rohit Kumar told AFP.

“This is the first time such an incident has occurred in this enclosure.”

The victim’s body was lying in a corner of the enclosure, draped in a white sheet, while the tiger had been taken away and locked up, an AFP reporter said.

The enclosure is separated from visitors by a concrete ditch, with shrubs on the tiger’s side followed by a 60cm railing.

The zoo has three white tigers, although only one of them is let out into the enclosure daily for visitors to see, a zoo official said.

White tigers are found in southern and eastern Asia, particularly India, and owe their appearance to a recessive gene. They are regarded as an endangered species.