Police in the central province of Quang Ngai announced that they had arrested two brother for allegedly assaulting a police officer during a routine traffic stop.
On Wednesday, Ba To District's traffic team signalled Bui Van Tai, 34, and his younger brother, 30-year-old Bui Thao to pull over for not wearing helmets.
But, they refused to obey the officer's instructions, police say.
The officers managed to pull the two men over down the road but both men refused to sign the ticket.
Instead, police say, they kicked over the officers' motorbike and threw stones at Sergeant-Major Dinh Quang Dai's head. However, because Dai was wearing a helmet he was not injured, police said.
The team called for back-up to control and escort the brothers to police station for questioning.
A report on the An ninh Thu do (Capital security) news website Friday said that as they were being placed into custody, Tai told his brother to take off his clothes to cause a stir.
The case remains under investigation.