A Florida prosecutor has filed a murder charge against the neighbourhood watch volunteer who shot and killed Trayvon Martin.

The case has captivated the United States and prompted civil rights demonstrations.

George Zimmerman, 28, was arrested and charged with second-degree murder in the death of 17-year-old Trayvon Martin, according to Angela Corey, the special prosecutor appointed by Florida's governor to investigate the racially charged case.

Mr Corey said at a news conference that Mr Zimmerman turned himself in to authorities, who then arrested him. He remains in police custody.

Mr Zimmerman, who is white Hispanic, said he acted in self-defence during a confrontation in a gated community in the central Florida city of Sanford on 26 February.

Police declined to arrest Mr Zimmerman, citing Florida's "Stand Your Ground" law, which allows people to use deadly force when they believe they are in danger of getting killed or suffering great bodily harm.

New York Mayor Michael Bloomberg and civil rights groups have launched a campaign to roll back "stand your ground" laws critics say led to the shooting death of Mr Martin.

The Second Chance on Shoot First campaign aims to reform or repeal laws on the use of deadly force in 25 states that Mr Bloomberg called "a license to murder".

The laws "justify civilian gunplay and invite vigilante justice and retribution with disastrous results," Mr Bloomberg told a news conference.

Others in the "Second Chance" effort include the National Urban League, the National Association for the Advancement of Colored People, the National Action Network and the online group ColorOfChange.org.