An Indian man diagnosed with throat cancer allegedly shot dead the colleague who introduced him to cigarettes.

Mustakeem Ahmad is said to have been consumed with rage at his co-worker after a doctor attributed the disease to his smoking habit.

The pair, both 25, worked as chefs at a restaurant in west Delhi owned by the alleged killer’s brother-in-law, according to the Hindistan Times.

Police said Ahmad also resented his colleague, named only as Inayat, because he was more successful at work.

He told detectives he purchased a pistol and practised firing it to ensure he killed the victim, who had been working at the restaurant for 18 months.

“Though Ahmad and Inayat were friends at the workplace, Inayat was reportedly better at his job and well-behaved and soon became the favourite of the restaurant owner,” said deputy police commissioner Sibesh Singh.

Ahmad was said to have taken up smoking cigarettes and marijuana under the influence of Inayat.

Mr Singh said: “In the course of time, Ahmad developed throat infection, forcing him to consult a doctor. Ahmad has claimed that the doctor told him he had developed throat cancer due to excessive smoking.”

Ahmad blamed his colleague for his cancer and tried unsuccessfully to get him sacked from his job, he added.

After his work performance deteriorated Ahmad was fired and investigators said he returned to his native village of Amroha in Uttar Pradesh, where he bought a gun and some cartridges.

“He first practiced firing in his village, before returning to Delhi a few days ago,” said Mr Singh. “He was carrying his loaded pistol to the restaurant and had planned to kill Inayat if he failed to get him fired from the job. That is what eventually happened. Ahmad ended up picking a fight with Inayat. He later shot at him in the middle of the argument,”

Inayat was rushed to hospital but died of his injuries.

Ahmad fled but was arrested in a police sting last week, as he visited a relative to borrow some money.