Police in Hoan Kiem District said it took place on Hang Buom Street at around 1:30 a.m. after the unidentified foreigners, who showed signs of drunkenness, started to verbally abuse a group of people sitting on the sidewalk.
It soon deteriorated into a physical confrontation, they said.
The Vietnamese threw beer cans and plastic chairs at one of the foreigners, who blocked them at first but then retaliated against one of the opponents.
No one reported the scuffle to them, but the police have launched an investigation nevertheless since foreigners were involved.