An inquest into the deaths of three IRA men killed in an SAS ambush needs to establish if there is an audio recording of the shootings, a coroner has been told.

A barrister for relatives of two of the three men shot dead in the incident in Coagh, Co Tyrone in June 1991 said there were unconfirmed claims that a tape was made but then destroyed.

Karen Quinlivan QC was addressing a preliminary hearing, sitting in Belfast's Royal Courts of Justice, ahead of this autumn's full inquest for Peter Ryan, Tony Doris and Lawrence McNally.

The men were intercepted as they drove through Coagh by SAS soldiers who suspected they intended to murder a member of the security forces.

All three were shot dead in a hail of gunfire.

Ms Quinlivan, who represents the Doris and Ryan families, said the key issue to be determined at the inquest was whether the use of lethal force was justified.

She was making submissions to coroner Mr Justice Michael Humphreys ahead of his deliberations on applications by the security forces for certain material to be withheld from the inquest on public interest immunity grounds.

The barrister insisted any information related to the apparent audio recording, and also on a video that was apparently taken in the aftermath, should be disclosed to the court.

"There was a film taken post-incident, we say that is relevant, it's the kind of matter that should be disclosed routinely," she said.

"More interestingly, there's a suggestion that there's an audio tape of the operation."

Ms Quinlivan said it had been further suggested that the audio tape no longer exists.

"Firstly, there needs to be confirmation as to whether a tape was made and how it was made, whether it exists, and if it was destroyed, in what circumstances was destroyed, who the decision was made by," she said.

The lawyer said even if the tape had been destroyed there was the possibility that notes had been taken by individuals who listened to it prior to its destruction.

"Even if the tape has been destroyed, it doesn't necessarily mean that there aren't records somewhere of what people noted was said in the tape," she said.

"So, inquiries shouldn't be totally confined to the tape."

Ms Quinlivan said around 148-150 rounds were fired during the incident.

"Some 72 rounds were deployed on Bloody Sunday, so it gives you an idea of the level of force used in this incident directed at a single vehicle," she added.

The full inquest is due to sit in Banbridge courthouse in September.