MOSCOW (AFP) - Russia opened an investigation on Saturday (Jan 9) after a hospital doctor was captured on video punching a patient with a blow that killed him instantly.

The shocking incident in the southern city of Belgorod raised questions over a cover-up culture in state medicine, with the investigation only opened days later after security camera footage was released on YouTube and aired on national television.

Belgorod's Investigative Committee said in the statement released on Saturday that the incident took place on Dec 29. It gave no explanation for the apparent delay in investigating the crime.

It said the doctor was suspected of causing death through negligence, for which he could serve up to two years in jail.

In the video, the strongly-built doctor in medical clothing drags the bare-chested male patient from the examination table, asking him "why did you touch the nurse?" and pushing him out of the doorway.

When the patient returns, the doctor deals him a single blow to the face and a crash can be heard as the middle-aged man falls backwards onto the floor.

Meanwhile, the doctor continues to scuffle with another man accompanying the patient, and it is only minutes later that the medics notice the patient lying motionless and attempt unsuccessfully to revive him.

The medics drag away the patient's body and then an orderly mops up blood stains.

The doctor hit the patient in the face after he "kicked a nurse during a procedure", the investigators said.

"The cause of death of the victim was trauma to the skull and brain from hitting the back of the head on the hard surface of the floor."

Russian media named the doctor as a surgeon at the hospital, Dr Ilya Zelendinov, and the patient as 56-year-old Yevgeny Bakhtin.

Health Minister Veronika Skvortsova has ordered the state health watchdog to carry out a check into the incident, state television reported on Saturday.

Russian medics have long operated in a culture of secrecy with patients having little recourse to compensation for medical errors.

Last year, two Russians resorted to taking guns to hospitals and shooting doctors dead for perceived mistakes in their treatment. Both killed themselves at the scene.