The gate of Fort Sam is still visible in Google Maps' Street View as it is on a public road Enlarge Image

Close-up, ground-level imagery of US military sites posed a "potential threat" to security, it said.

The move follows the discovery of images of the Fort Sam Houston army base in Texas on Google Maps.

A Google spokesman said that where the US military had expressed concerns, images had been removed.

Google has now been barred from filming and conducting detailed studies of bases, following the discovery of detailed, three-dimensional panoramas online - and in particular, views of the Texan base.

But images inside the base have been removed

"Images include 360-degree views of the covered area to include access control points, barriers, headquarters, facilities and community areas," said the defence department in a statement quoted by AFP news agency.

It said such detailed mapping could pose a threat.

Google spokesman Larry Yu said the decision by a Google team to enter the Texas base, which is in San Antonio, and undertake a detailed survey, had been "a mistake".

He told the BBC that it was "not our policy to request access to military installations, but in this instance the operator of the vehicle with the camera on top - which is how we go about capturing imagery for Street-View - requested permission to access a military installation, was given access, and after learning of the incident we quickly removed the imagery".

Individuals and governments

Military officials are currently looking into exactly what imagery is available - though it may not be able to order its removal if images are taken from public streets.

'SPY' IN THE SKY Mar 2008: Pentagon bans Google map-makers filming inside military bases Feb 2008: Heathrow expansion protesters use Google Earth (GE) to plan House of Commons rooftop demo Oct 2007: Al-Aqsa Martyrs' brigade reportedly using GE to plot rocket attacks on Israel July 2007: New Chinese Jin-class nuclear sub spotted in port by users of GE Feb 2007: India demands sensitive sites be blurred amid concern over extremists Aug 2006: Morrocco begins blocking access to GE, giving no reason Dec 2005: GE obscures view of Washington mansion of Vice-President Dick Cheney Aug 2005: South Korea voices "security concerns" at images of its military bases and presidential mansion

Among the popular mapping services offered by Google are Street View, which allows web users to "drive" along virtual US landscapes with ground-level views, and Google Earth, which offers detailed satellite and 3D images of locations around the world.

In this case, it was imagery offered on Street View that caused the concern.

But both have provoked complaints - from individuals depicted in the images and from governments concerned that satellite images could compromise security.

Gary Ross, a spokesman for the US Northern Command, told AFP that although such services could be useful, "there has to be a balance".

But Mr Yu said Google would listen to concerns about privacy and security.

"We try to have a compliant image removal policy - not only relative to the military but to consumers also," said Mr Yu.

"If people have concerns, they should contact us."