AN investigation is underway after dozens of paratroopers were filmed watching on as soldiers engaged in an orgy with a woman at their barracks.

In footage seen by the Gazette and circulated on social media, a number of men, all soldiers with 16 Air Assault Brigade, are seen engaging in sex acts with a red-headed woman.

An army source told the Times newspaper the clips were "pretty graphic in detail", adding: “It’s a single female with a number of soldiers engaged in consensual sex.”

It is believed the woman is a civilian who may have been smuggled in to Merville Barracks in Colchester.

READ MORE: Colchester-based paratroopers reportedly 'had orgy' at barracks

The footage shows sexual activity in different areas of the base, some acts taking place in private rooms and others in communal areas.

It remains unclear when the incident took place.

During one piece of footage a serviceman gives a salute as he has sex with the woman.

In another piece of footage a serviceman spits on the woman and calls her a "tramp".

Gazette: Colchester's Merville BarracksColchester's Merville Barracks

The Royal Military Police is said to be investigating the incident, probing how the woman got onto the base.

The RMP is also said to be investigating whether the woman was signed in, and officers will assess whether any illegal activity took place - including whether the woman was a sex worker.

Army sources told the Times the men may be disciplined for breaking standing orders if they are found to have done anything wrong.

A spokesman for the army said: “The army expects the highest standards of behaviour from all their personnel.

"Anyone not maintaining these standards will be investigated and appropriate action will be taken against them.

“The Royal Military Police are investigating several videos appearing to involve army personnel.

"It would be inappropriate to comment further while investigations are ongoing.”