Posting naked pictures of an ex-partner online can now land you in jail for up to six months in California, after a bill against so-called "revenge porn" was signed into law.

The legislative bill went into effect immediately after state governor Jerry Brown signed it Tuesday. Anyone convicted of "illegally distributing private images with the intent to harass or annoy" could also face a fine of up to $1000.

"I want to thank Governor Brown for recognizing that this bill was needed," said state senator Anthony Cannella, who proposed the legislation including an "urgency clause" to fast track it into force.

"Until now, there was no tool for law enforcement to protect victims .. Too many have had their lives upended because of an action of another that they trusted," he added.

Legislation already exists against posting unauthorized pictures of other people which invade their privacy, but the new California law covers pictures that were taken with consent, for example when a couple was together, but which are later posted online without the ex-partner's agreement.

"Revenge porn often begins when relationships end," said Cannella, who noted that there are even websites which "specialize in posting such materials, and charge the subjects unreasonable fees to take down the illicit photos."

Dr. Charlotte Laws, whose daughter was a victim of revenge porn, said: "I am thrilled to see California taking a leadership role in protecting victims of revenge porn."

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© 2013 AFP