A Russian military attack helicopter has accidentally fired on spectators during war games in western Russia, reportedly injuring several people.

The Russian military acknowledged a helicopter accidentally fired a missile during drills, but insisted no-one was hurt in the incident and refrained from saying when it happened.

The video released on the online 66.ru, RBC and Life.ru news portals showed a pair of Ka-52 helicopter gunships sweeping low, with one of them firing a rocket that explodes next to a spectator in a parking lot.

The 66.ru website said two people were seriously wounded and two vehicles were destroyed in the incident during the Zapad (West) 2017 manoeuvres.

It said the accident happened on Sunday or Monday (local time) at the Luzhsky range, about 100 kilometres east of the border with Estonia.

The news portal said the video was provided by an unidentified witness.

Russian helicopters take part in manoeuvres at the Luzhsky range, where the misfire occurred. ( AP: Ivan Sekretarev )

Life.ru said the incident happened at the Luzhsky range on Saturday and the rocket exploded near a crowd of journalists, military experts and foreign military attaches. It said three people were hurt.

It said a preliminary investigation stated the incident was caused by a short-circuit in the helicopter's electric system that resulted in the accidental launch of the rocket.

RBC also reported that the incident happened on Saturday.

It said that three people were injured and said they were soldiers.

Putin attended drills

Russian President Vladimir Putin attended the drills at the range on Monday accompanied by the top military brass.

The Russian military's Western Military District acknowledged on Tuesday that the video was genuine.

It denied it happened on Monday, but didn't specify when or where the incident in the video took place.

It insisted that no-one was hurt, and just one military truck was damaged.

The military said the incident was caused by the failure of the helicopter's targeting system.

The Zapad 2017 manoeuvres, held jointly by Russia and Belarus, got underway on Thursday at several firing ranges in both countries and run through Wednesday.

The drills have rattled some NATO members, including the Baltic states and Poland, who have criticised an alleged lack of transparency about the war games and questioned Moscow's intentions.

AP