US state outlaws 'upskirting' photos

The US state of Massachusetts has outlawed people from taking secret photographs up women's skirts, making it a crime punishable by two-and-a-half years in prison and a fine of $US5000 ($A5500).

Democrat state governor Deval Patrick signed the law two days after a court ruled that a man hadn't acted illegally by taking such photographs of a woman on the Boston subway.

It was not immediately clear whether the northeastern state is the first in the US to criminalise the specific phenomenon called "upskirting" but the law comes into effect immediately.

It makes "the secret photographing, videotaping, or electronically surveiling of another person's sexual or other intimate parts, whether under or around a person's clothing... a crime", Patrick's office announced in a statement, outlining the basic penalties.

In addition, those who commit the offence on a child could face twice as long in jail - up to five years in a state prison, as well as the $US5000 fine.

A spokesman in Patrick's office told AFP that the new law was passed in response to the recent court decision and not copied from legislation adopted in other states.