Melbourne, Oct 2 (ANI): An Oz couple, who were arrested and were being taken to a Territory cop station in a police paddy wagon, were seen shagging in the back of the vehicle by another motorist.

Hannah Walker, 18, was driving behind the police car and was shocked to find the couple bonking in the back when she pulled up behind them at a red light.

Walker was travelling along Gilruth Avenue towards Darwin city when she stopped at the traffic lights that meet Goyder Rd in Parap outside Darwin High School and saw the pair pashing about 5pm on September 30.

"I saw the two people kissing and thought 'geez, in the back of a paddy wagon - they're keen'," the Northern Territory News quoted her as saying.

She said by the time she reached the next set of lights and got stuck behind the police car again the couple were having sex.

"It was a red light and I had to sit behind the paddy wagon for a few minutes," she said.

"I couldn't believe it when I saw them just going for it. There was a woman laying on the floor and a man on top. They had clothes on but from their movements you could tell they were having sex.

"I could see the officer in the side mirrors and he had no idea what was going on," she stated.

Walker followed the police car most of the way to her home in Larrakeyah and said it turned down Mitchell St towards the Watch House.

NT Police Darwin watch commander Senior Sergeant Daniel Shean said the police were not aware of any sexual acts being performed in the paddy wagon.

But he said the couple had been taken into protective custody to sober up.

"I have spoken with the members involved and they said they did see the couple kissing but did not see any nudity or anything to indicate they were having sex," he said.

But he admitted it is hard for officers to see everything that goes on in the back - and urged anyone who witnesses any untoward happenings in the back of a paddy wagon to call police on 131 444.

"If they report it immediately we can ... address it straight away," he added. (ANI)