Miami Heat basketball players posed in "hoodies" in a picture published on Friday to protest against the Florida shooting death of an unarmed black teenager by a neighborhood watch volunteer who said he was acting in self-defense. Leading Heat player LeBron James posted a picture on his Twitter account showing the National Basketball Association team in their training tops - all with the hoods raised over their heads in the fashion reportedly worn by Trayvon Martin on the night he was shot last month.

Police in the central Florida town of Sanford where Martin was killed have not arrested the neighborhood watch volunteer, George Zimmerman, citing the state's controversial "Stand Your Ground" law, which allows people to use deadly force when they perceive danger in a public place.

The case has rippled across the nation and prompted rallies protesting the failure of the police to arrest the shooter and, more broadly, a pattern of racial discrimination black leaders cite in Sanford and elsewhere in the country. James, who was playing in Orlando, Florida, around 20 miles from Sanford on the night when Martin died, attached hashtags to his twitter post which made clear his motive for posting the picture, including "#Stereotyped" and "#WeWantJustice."

James' teammate Dwyane Wade also switched his twitter profile to a portrait of himself wearing a hoodie, and has lent his support to a petition demanding 'justice for Trayvon Martin'.

"The NBPA is saddened and horrified by the tragic murder of Mr. Martin and joins in the chorus of calls from across the nation for the prompt arrest of George Zimmerman," the NBA players' union, the NBPA, said in a statement after the Heat protest.

It also called for the permanent resignation of Sanford Police Chief Bill Lee and a probe into what it described as racial bias by the police in the matter.

"Their silence in the face of this injustice is reprehensible and they cannot be trusted to safe guard the citizens of the Sanford community equally," the statement said.