Doctors in northern India have surgically removed 40 knives from the stomach of a man who had swallowed them over the past two months.

The 42-year-old man is recovering in a hospital in Punjab state after undergoing surgery in which doctors removed the knives — some folded and some with exposed blades up to 18cm long.

Jatinder Malhotra, a doctor who was present during the five-hour operation, said the man, who works as a police constable, was apparently suffering from a psychiatric disorder and is now being counselled.

He said the man could not explain why he swallowed the knives.

Malhotra said he had never before heard of a case of a person swallowing knives.