Zoo officials said that the tiger had been unwell since July. (Representational)

An animal keeper at a zoo in Delhi was attacked by an "unwell and distressed" Bengal tiger when he went to fill its water bowl today morning, officials said.

The zoo's curator said the employee suffered minor injuries in the attack.

Zoo keeper Fateh Singh was on a night shift and had gone to fill the tiger's water bowl. The tiger swooped down on him from inside the cage.

"The eight-year-old tiger is unwell. A team of doctors from Indian Veterinary Research Institute in Bareilly and the zoo's Director Renu Singh examined the animal late in the night on Monday," the zoo curator said.

"Late night inspection may have rattled the tiger. Such incidents have happened in the past too," he said.

The zoo's staff took Fateh Singh to a hospital, where he got a few stitches.

"The tiger has been unwell since July 27. It was only on August 14 that an inspection was conducted by the Delhi zoo veterinary officer," an official said.

Thereafter, the animal was kept in a squeeze cage for examination purposes. Frequent check-ups in the squeeze cage have agitated the tiger, he claimed.