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.