Out on bail ... George Zimmerman, left.

Out on bail ... George Zimmerman, left. Photo: Reuters

Neighbourhood watch volunteer George Zimmerman has been released after posting $US150,000 ($145,000) bail after US authorities charged him with second-degree murder for shooting unarmed black teen Trayvon Martin.

His release from a Florida county jail today came after a Florida judge presiding over the case heard arguments during a bail hearing on Friday.

Television networks showed Zimmerman dressed in jeans and a brown jacket walking out of the jail in Sanford, Florida, accompanied by an unidentified man.

Killed ... Trayvon Martin.

Killed ... Trayvon Martin.

Neither of the two made any statements.

AFP