Police said they believe that money disputes were behind a case where a woman was forced into a vehicle outside Stanley Prison on Saturday.

At a press briefing on Sunday, the force said they received a report at around 10am the day before that a woman was taken by four people into a van which then fled the scene, despite efforts by two Correctional Services Department officers and some passers-by to stop them.

Officers said they intercepted the van near Ocean Park 15 minutes later.

Four people were arrested on suspicion of false imprisonment, assault causing actual bodily harm and dangerous driving.

Chief Inspector Wong Yu-fai said the victim, 32, was attacked in the incident, with her head and limbs being scraped, while a Correctional Services Department officer was hit on the head as they tried to help the woman.

Wong said the victim had money disputes with four people, at least two of them teenagers.

"The police believe that the victim and the four arrested have been friends for more than a year, and that the motive had to do with money disputes that involved hundreds of thousands [of dollars]," he said.

He added officers would look into whether other people were involved.