Google has upgraded its Android Maps app so it can provide directions when not connected to the internet.

The software also lets devices find businesses' locations, opening hours and telephone numbers while offline.

The firm said tourists visiting places outside their mobile subscription plans and people living in emerging markets, where data can be expensive, would be among those who would benefit most.

But one expert said budget-phone owners would now have to juggle data.

"Entry-level Android smartphones sometimes only have four gigabytes of onboard storage, making it a precious resource," commented Ben Wood from CCS Insight.

"Once you've downloaded a few applications, some music and perhaps a video, that memory quickly disappears.

"So some users may find using map downloads limits what else they can do with their device - but to be honest that's one small negative in a sea of positives about this update."

Google said downloading most of Greater London would take up 380 megabytes on a device, while storing the San Francisco Bay area would require about 200MB.

It added that it intended to release a similar update for iOS devices "very soon", but could not confirm if that would be before the year's end.

To make use of the new feature, users will have to tell the app to download an area they select.

Once the information has been installed, the app is designed to switch "seamlessly" between offline and online modes unless forced to stay off the net.

That means, for example, that if a driver starts their journey in an underground garage without a data connection, the app will suggest a route and drive-time estimate based on typical conditions, but will then amend the advice once it gains access to live traffic and accident information.

The offline map will automatically update once every 15 days to stay current so long as the handset is plugged into a charger and connected to wi-fi, unless the user overrides these restrictions.

BBC News