The unnamed couple, a 28-year-old man and a 22-year-old woman, were caught in the act late on Easter Sunday by traffic police on the E18 highway, some 25 miles west of Oslo.Officers who clocked the couple's silver Mazda 323 racing at 133 kilometres per hour in a 100 zone realised they were doing more than just breaking the speed limit, police told AFP.

"It was veering from one side to the other because the woman was sitting on the man's lap while he was driving and doing the act, shall we say," said Tor Stein Hagen, a superintendent with Soendre Buskerund district police.

"He couldn't see much because her back was in the way," he added.

"Why they did it on a highway with such a high risk we don't know."

After following the couple for nearly a kilometre, officers pulled the car over at a service station.

"We have taken away his driving licence because of the danger that he caused," Mr Hagen said.

Prosecutors will decide within the next week what his punishment will be, with police having filmed the incident to use as evidence against the driver.

Mr Hagen said he expected the man to face a fine of "several thousand Norwegian crowns" and a lengthy driving ban.