A prominent South African MP fired his gun to fend off a violent attack by a gang on him and two of his colleagues in Cape Town.

Ian Cameron - along with two other members of parliament's police committee, Lisa Schickerling and Nicholas Gotsell - were returning from a work trip when their vehicle was ambushed in the township of Philippi on Tuesday.

The assailants smashed the car's windows with bricks, injuring Cameron and Gotsell.

Cameron, whose teeth were broken, retaliated by opening fire, injuring one of the attackers.

Police said two teenagers, aged 16 and 18, had been arrested while they investigate a case of attempted murder and attempted hijacking.

Crime is a major problem in South Africa and the country has one of the highest murder rates in the world.

One of the suspects was apprehended while seeking medical treatment at a hospital on Tuesday, while the other was arrested on a farm early on Wednesday, police said, adding that a search was under way for a third suspect.

Cameron, who chairs the police committee, told broadcaster Newzroom Afrika that they were returning from an unannounced visit to a police academy in Philippi when "the first brick came through [the window]" on the driver's side and hit him in the face.

Cameron said that while he was trying to fend off his attacker, he saw his colleagues also face a barrage of attacks from the other assailants.

"I realised that if we don't do something, then this can go really bad. So I did my best to act in self-defence with my firearm and then we sped off to the closest secure location."

In South Africa, it is legal to carry a firearm, so long as you have a licence.

Cameron, who was seen with a cut lip in the interview, said some of his teeth had been broken, while Gotsell was briefly hospitalised after he was hit on the head.

Gotsell, speaking after being discharged from hospital, praised Cameron, saying he "acted with such bravery".

All three MPs are members of the Democratic Alliance (DA), the second-biggest party in South Africa's coalition government.

The party said the attack showed how "out-of-control" crime is in South Africa.