President Barack Obama has said that the death of Trayvon Martin, an unarmed black teenager shot dead in Florida last year, has raised questions about why young African-Americans experience racial profiling.

"You know, when Trayvon Martin was first shot, I said that this could have been my son. Another way of saying that is Trayvon Martin could have been me, 35 years ago," Obama told reporters at the White House on Friday, in his first public remarks after the acquittal by a Florida court of Martin's shooter, George Zimmerman.

Jurors found that Zimmerman, who identifies himself as Hispanic, was acting in self-defence when he shot the unarmed black teenager.

Obama, the first black American to become president, usually does not speak about race.  On Friday’s briefing he said it is time "for all of us to do some soul searching”. On the positive side, Obama  said race relations in the United States actually are getting better.

Once the jury has spoken, that is how our system works

Barack Obama, US president

The president declined to wade into the detail of legal questions about the Florida case, saying, "Once the jury has spoken, that is how our system works.''

But he said state and local laws, such as Florida's "stand your ground'' statute, need a close look.

He questioned whether a law that sends the message that someone who is armed "has the right to use those firearms even if there is a way for them to exit from a situation'' really promotes the peace and security that people want.

Obama also raised the question of whether Martin himself, if he had been armed, "could he have stood his ground on that sidewalk'' and shot neighbourhood watch volunteer George Zimmerman if he felt threatened when being followed.

The widely followed Trayvon Martin case has prompted a discussion in the United States about race and self-defence laws.

US Attorney General Eric Holder has said the Justice Department has an open investigation into the case.

The department is looking into whether Zimmerman violated Martin's civil rights.