It is unavoidable that civilians will die in the crossfire between police and criminals, Deputy Police Minister Fikile Mbalula said as government on Thursday vowed to change the law to encourage police to use lethal force when necessary.

"In the course of any duty the innocent will be victimised," Mbalula told reporters in Parliament.

"In this particular situation where you are caught in combat with criminals, innocent people are going to die not deliberately but in the exchange of fire. They are going to be caught on the wrong side, not deliberately, but unavoidably."

He said there had always been collateral damage in the fight against crime and a recent spate of civilian deaths at police hands could not be blamed on the ministry's call for law enforcers to return fire when confronted with dangerous criminals.

"We cannot say to the police, retreat. We cannot say to South Africans, despair. Our job is to give people hope.

"Yes. Shoot the bastards. Hard-nut to crack, incorrigible bastards."

President Jacob Zuma said the government planned to "expedite" changes to Section 49 of the Criminal Procedure Act in a bid to "limit the number of police killed by criminals".

Answering questions in the National Assembly, Zuma said the violent nature of crime in South Africa made it imperative to modify the law to give police greater clarity on when they can shoot to kill.

"The crime in South Africa is different from other countries ... it is different from the point of the view that this one is violent, more violent than in any other part of the world.

"We are saying we need to fight crime and that when criminals are cornered they take out guns. They don't warn, they kill, and many police have died as a result of that.

"On that spur of the moment, what do you do as a policeman? Should you say, because I'm a very good policeman I am here, I have got a gun, but I am not going shoot you?"

Responding to concerns from the Democratic Alliance that the law change could see a return to the practice of "shooting unarmed citizens in the back", Zuma said the amendment would be in line with the Constitution.

"The technical amendment of Section 49 will take cognisance of the founding principles of our Constitution. The exact wording of this amendment is being finalised."

Mbalula said the amendment expected to be tabled in Parliament next year would not amount to an overhaul of the act.

Lawmakers would change the act "in terms of emphasis on the word 'necessary'" to remove ambiguity in the law. Neither Mbalula nor Zuma gave further details.

Section 49 states that if someone suspected of a serious crime resists arrest, the police may "use such force as may in the circumstances be reasonably necessary to overcome the resistance or prevent the person concerned from fleeing".

It also gives police the right to use lethal force if their lives or those of innocent bystanders are in danger.

Police Minister Nathi Mthethwa, Mbalula and national commissioner Bheki Cele have all suggested that the act puts too heavy a discretionary burden on the police.

Opposition to changing a law that owes its post-apartheid form to a Constitutional Court judgment mounted after the police shot dead a toddler in Midrand on Saturday.

They mistook a metal pipe for a gun and killed three-year-old Atlegang Aphane. A constable was arrested.

The Centre for the Study of Violence and Reconciliation has said it feared such incidents were the result of "an overall breakdown of control over the use of lethal force within the [South African Police Service]".

Constitutional law expert Pierre de Vos said there was little leeway to change the act without falling foul of the Constitution.

He said that regardless of any change of wording, the police would always have to make split second decisions on whether it was justified to use lethal force.

"Those decisions can only be good decisions if the police are properly trained. So I think they are trying to change the law instead of fixing a bigger problem which is that we need real police training," he told Sapa

Zuma acknowledged that police officers' were not adequately trained on the use of deadly force.

"Therefore the proposed amendment that seeks to provide more clarity, needs to be complemented by training of all police officers on relevant sections of the legislation," he told MPs.