The police fired a live round in Ho Man Tin on Tuesday afternoon as they arrested seven men on suspicion of conspiracy to commit robbery and possessing offensive weapons.
Two unmarked police vehicles collided with a stolen taxi and another car as officers moved to intercept the suspects on Sheung Lok Street.
Police said one officer fired a shot when the car was driven at him. The bullet didn't hit anyone, but police said three suspects were injured while being arrested.
The force said it believes the men, aged between 20 and 27, were heading to Hung Hom to commit a robbery.
Detectives were also looking into whether the men are linked to jewellery store robberies that took place on Sunday and Monday.
Officers said they seized five knives, a large hammer, masks and gloves from the cars.