The President of the Philippines Rodrigo Duterte, who has presided over an unprecedented drug war, killing thousands since he was elected in May, has called innocent people and children caught up in the violence "collateral damage".

Duterte said police in the Philippines could kill hundreds with impunity firing off rounds with an M16. He said it was understandable that a police officer with an automatic weapon would kill as many as a thousand while pursuing on gangster.

"When they meet, they exchange fire. With the policeman and the M16, it's one burst, brrr, and [he] hits 1,000 people there and they die," the president told al-Jazeera.

"It could not be negligence because you have to save your life. It could not be recklessness because you have to defend yourself."

In the past Duterte has rebuffed international criticism of his drug war saying his crackdown on the narcotics trade bears no comparison with wars waged by the US and its allies in Iraq, Afghanistan and Vietnam.

Repeating the claim, Duterte said: "When you bomb a village you intend to kill the militants but you kill the children there... Why do you say it is collateral damage to the West and to us it is murder?"

At least 3,800 people have been the victim of extrajudicial police and vigilante killings.

Amid the impunity of Duterte's drug war, officials have accepted at face value the accusation that all those caught up in the drug war have been involved in the production, sale and consumption of drugs.

Rodrigo Duterte
Rodrigo Duterte inducts new officers of a business group during a meeting in Pasay city, Metro Manila, Philippines on 13 October Erik De Castro/Reuters

However, it is alleged that under the cover of killings, criminals and police officers have settled old scores with those who may have nothing to do with the narcotics trade.

"We have three million drug addicts and it's growing. So if we do not interdict this problem, the next generation will be having a serious problem," Duterte said.

"You destroy my country, I'll kill you. And it's a legitimate thing. If you destroy our young children, I will kill you. That is a very correct statement. There is nothing wrong in trying to preserve the interest of the next generation," he added.