BRUSSELS, Belgium - European Union data privacy regulators are telling Google to warn people before it sends cameras out into cities to take pictures for its Street View maps.

In a letter to the company, regulators also say Google should shorten the time it keeps the original photos from one year to six months.

In a statement, Google says its need to retain Street View images for one year is "legitimate and justified."

The company says it also already posts notifications on its website about where its Street View cameras are clicking.

The alert system on Thursday indicated Google's picture-taking vehicles have been cruising the streets of Cagiliari, Italy, Nantes, France and possibly other nearby cities.

Street View launched in the U.S. in 2007 and now adds photos of real-life street scenes to Google's maps of around 100 cities worldwide. To soothe privacy concerns, it uses special software to blur pictures of faces and car licence plates.