George Zimmerman, the neighborhood watch volunteer charged with second-degree murder for shooting an unarmed black teen, was released early Monday after posting a $150,000 bond, US media reported.

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

Neither of the two made any statements.

Images showed the men walking toward a car and then driving away to an unknown destination.

The release came after a bail hearing on Friday.

If convicted, Zimmerman could face life in prison.

Prosecutors say the teen Trayvon Martin was simply "minding his own business" when he was accosted and shot dead by Zimmerman after buying some candy and a bottle of ice tea from a local store in Sanford.

During the hearing Zimmerman told police he had been tracking Martin after viewing him as suspicious but shot purely in self-defense after being assaulted.

Prosecutor Bernie De La Rionda urged the Florida judge to deny bail or at least put it at $1 million but the defense suggested the price for Zimmerman's release until his yet unscheduled trial should be $15,000.

After hearing arguments from both sides, Judge Kenneth Lester set bail at $150,000 but imposed conditions including electronic GPS tracking, a curfew from 7:00 pm until 6:00 am, and a requirement for him to report every three days to the authorities.

"There is to be no contact with the victim's family. There is to be no possession of firearms, be they rifles, shotguns, handguns, pistols, revolvers, any type of firearm or destructive device. There is to be no consumption of alcohol," Lester said.

Authorities are also seeking to put in place arrangements for Zimmerman to live outside Florida pending the trial.

Both he and his family, who testified via video link for their own safety, have received threats.

Police initially decided not to press charges against Zimmerman, setting off a storm of protests in the black community. The man was only charged last week after a special prosecutor's investigation.

The case drew an emotional reaction from President Barack Obama after sparking demonstrations around the country as Martin's family, lawyers and civil rights leaders alleged he was a victim of racial profiling.

At Friday's hearing, defense attorney Mark O'Mara sought to challenge the prosecution's account of what happened between Zimmerman and Martin that led to the shooting.

"He came in voluntarily and surrendered himself to law enforcement. He is well established in the community," O'Mara said.

Dale Gilbreath, an investigator in the case, acknowledged that there was no direct evidence of who threw the first blow in the confrontation, other than the fact that Zimmerman had been following Martin.

Zimmerman's wife Shellie was steadfast in her husband's defense, telling the court: "Absolutely he is not a violent person or a threat to the community."

O'Mara told journalists after the hearing that the family had trouble coming up with the bond.

Zimmerman's wife testified that the couple had no assets or income to put toward a bond.

The suspect's father said he was prepared to take out a second mortgage on his house to help raise the money.