Ferguson police officer Darren Wilson says he could not have done anything differently to prevent the fatal shooting of black teenager Michael Brown.

It comes as protests took place across America on Tuesday night in response to a grand jury ruling over the case.

Mr Wilson, who was told on Monday he would not face charges over the 18-year-old's death, broke his silence in an interview with ABC News.

He said he had a "clean conscience" because "I know I did my job right".

Asked about witness claims that Mr Brown put up his hands, Officer Wilson said: "That would be incorrect. No way."

Describing the August incident, the 28-year-old said: "I take out [my gun] and point it at him and what I said was 'Get back or I'm going to shoot you.'

"Immediately he grabbed the top of my gun. When he grabbed it he said 'You're too much of a p***y to shoot me.'

"While he is doing that I can feel his hand coming over my hand and get inside the trigger guard. He tried to shoot me with my own gun."

Officer Wilson added that Mr Brown was a "powerful man" who "wanted to kill me".

The interview follows the release of Officer Wilson's testimony in which he said Mr Brown, who had been unarmed, looked like a "demon" during their altercation.

Grand jury

After hearing 70 hours of evidence from about 60 witnesses, a grand jury decided there was "no probable cause that a crime had been committed".

Their decision sparked violent protests in Ferguson, which continued into a second day.

St Louis prosecutor Bob McCulloch said some witnesses had admitted giving statements based on what they "assumed" had happened or "repeated what they had heard on the street".

Forensics showed Officer Wilson fired 12 shots at the teenager, but suggested he had acted in self-defence during a struggle.

The US Justice Department is conducting a separate investigation into possible civil rights violations that could result in federal charges against Officer Wilson.

Missouri governor Jay Nixon increased the National Guard presence to 2,200 troops to try and quell violent protests that erupted on Monday after the grand jury decision.

The ramping up of security did not stop hundreds of angry demonstrators gathering outside the city hall before overturning and torching a patrol car.

Police responded by firing tear gas and numerous arrests have been made.

The crowd has now dispersed.

The continued protests came as Barack Obama announced a nationwide campaign to make sure law enforcement in the US was "fair".

But the President said he had "no sympathy" for people "destroying their own community" through anger at the police.