A group of 20 heavily-armed Mekamui supporters in the Papua New Guinea province of Bougainville have held up and seized a police vehicle at a roadblock at the weekend.
The province's police chief assistant commissioner, Joe Bemu, says the men were armed with knives and high-powered weapons and fired shots in the air.
He says they ordered the four policemen out of the vehicle and demanded money for violating the Mekamui "No Go Zone".
When the policemen failed to produce the money the men took the keys and ordered the police to walk.
Later negotiations with Mekamui's representatives led to an increased request for cash.
Mr Bemu says the government is negotiationg the vehicle's release with the Mekamui group.