The European Commission has launched a preliminary inquiry into Google's search engine and advertising business.
The EC confirmed that it has asked Google to comment on three complaints against its business practices, but has not yet opened a formal investigation.
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The complaints came from British price comparison site Foundem, French legal search engine ejustice.fr and Microsoft's Ciao from Bing.
"As is usual when the commission receives complaints, it informed Google earlier this month and asked the company to comment on the allegations," the EC said. It said it was working closely with national competition authorities on the case.
A Google spokesman said, "At this stage this is a fact-finding exercise and we are happy to answer the commission's questions. We are happy to explain our products and technology, and are very confident that our business operates in the interests of users and partners, as well as within European competition law."
The complaints relate to how Google ranks search results. In a blog post, Julia Holtz, Google's senior competition counsel, said each case raised slightly different issues.
"The question they ultimately pose is whether Google is doing anything to choke off competition or hurt our users and partners. This is not the case," she said.
Holtz said she believed Google's business practices reflected a commitment to put its users' interests first and to compete fairly and squarely.
However, Google also faces legal problems in Italy where staff have been accused of violating users' privacy and criminal defamation.
The case relates to a video posted in 2006 that showed students at a Turin school bullying an autistic schoolmate.
Google said it took down the "totally reprehensible" video within hours of being notified by the Italian police. It also worked with police to identify the person responsible for uploading it. She and several classmates were later sentenced to 10 months community service.
Google said its involvement normally ended there, but a Milan public prosecutor had decided to indict four Google employees on charges of criminal defamation and a failure to comply with the Italian privacy code.
"None of the four Googlers charged had anything to do with this video," Google EMEA VP and deputy general counsel Matt Sucherman said in a statement. "They did not appear in it, film it, upload it or review it. None of them know the people involved or were even aware of the video's existence until after it was removed."
Even so, three of the four were convicted for failure to comply with the Italian privacy code. But all four were acquitted of criminal defamation.
"In essence, this ruling means that employees of hosting platforms like Google Video are criminally responsible for content that users upload," Sucherman said, adding it intended to appeal the "astonishing decision" because the Google employees on trial had nothing to do with the video in question. "It is outrageous that they have been subjected to a trial at all," Sucherman said.
Google is also worried that the judgment undermines European "safe harbour" legislation, which absolves hosting firms from criminal liability provided they act instantly against illegal content posted on their systems.
The judgment "attacks the very principles of freedom on which the internet is built", Sucherman said. "The belief, rightly in our opinion, was that a notice and take down regime of this kind would help creativity flourish and support free speech while protecting personal privacy.
"If that principle is swept aside and sites like Blogger, YouTube and indeed every social network and any community bulletin board, are held responsible for vetting every single piece of content that is uploaded to them - every piece of text, every photo, every file, every video - then the web as we know it will cease to exist, and many of the economic, social, political and technological benefits it brings could disappear."