By Foo Yun Chee

BRUSSELS (Reuters) - EU regulators, investigating Google for alleged anti-competitive behavior, want the internet search giant to offer concessions that cover all platforms, including computers, tablets and mobile devices, two people familiar with the issue said on Friday.

If Google is not able to provide satisfactory concessions, it will face charges and potentially severe fines, the EU's competition commissioner, Joaquin Almunia, has said.

Almunia wants remedies for all computing devices that have access to the Internet and provide a search capability, one of the people said.

Mobile devices and tablets are increasingly becoming gateways to the Web and Web-based content such as movies and music.

Earlier this month, the world's most popular search engine proposed concessions in a bid to settle an 18-month long investigation fueled by complaints from rivals including Microsoft. Neither Google nor the EU have said what those concessions were.

The European Commission is now examining the offer. The EU watchdog has said Google may unfairly favor other Google services over rivals and may have copied material from other websites, such as travel and restaurant reviews without permission.

It is also concerned that Google's advertising deals may exclude third parties from concluding similar deals with rivals while contractual restrictions on software developers may prevent advertisers from transferring their online campaigns to rival search engines.

Companies can be fined up to 10 percent of their turnover for breaching EU rules. In Google's case, that could reach $4 billion based on its 2011 results.

(Reporting by Foo Yun Chee; Editing by Mark Potter)