BRUSSELS — European Union data privacy regulators are telling Google Inc. to warn people before it sends cameras out into cities to take pictures for its Street View maps, adding to the company's legal worries in Europe.

Google should shorten the time it keeps the original photos from one year to six months, regulators also said in a letter to the company obtained by The Associated Press yesterday.

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

The company, based in Mountain View, Calif., said it also already posts notifications on its Web site about where its Street View cameras are clicking. The alert system yesterday indicated Google's picture-taking vehicles have been cruising the streets of Cagliari, Italy, 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 license plates.

Google has been slow to roll out the service in Europe after governments raised concerns that taking pictures of people in public places could break some EU rules on personal privacy.

Greece told the company last year to halt plans to snap the nation's streets until more privacy safeguards are provided and in April, residents of one English village formed a human chain to stop a camera van.

Google has also bowed to German demands to erase the raw footage of faces, house numbers, license plates and individuals who have told authorities they do not want their information used in the service.

EU Justice Commissioner Viviane Reding said that Europe had "high standards for data protection" and that she expected that "all companies play according to the rules of the game."

The head of EU data protection agencies, Alex Turk, told Google's data privacy chief Peter Fleischer in a letter dated Feb. 11 that the company should always give advance notice on its Web site and in the local or national press before it takes pictures.

It should take care to avoid taking pictures "of a sensitive nature and those containing intimate details not normally observable by a passer-by," Turk said.

He also said the company should revise its "disproportionate" policy of keeping the original unblurred images for up to a year, saying improvements in Google's blurring technology and better public awareness would lead to fewer complaints — and a shorter delay for people to react to the photos they see on the site.