European regulators said on Wednesday that they are investigating complaints filed by three web companies that contend the US Internet giant Google is not playing fair.
The European Commission "can confirm that it has received three complaints against Google which it is examining," said a statement from Brussels, spelling out that the probe remains informal at this stage.
"As is usual when the commission receives complaints, it informed Google earlier this month and asked the company to comment on the allegations," it added.
A senior Google executive said in a blog post late on Tuesday that complaints were made by British price comparison website Foundem, French legal search engine ejustice.fr, and Microsoft's Ciao! from Bing.
"Though each case raises slightly different issues, the question they ultimately pose is whether Google is doing anything to choke off competition or hurt our users and partners," senior Google competition counsel Julia Holtz said.
Google said it will provide information to the commission and was confident its operations conform to European competition law.
Foundem and ejustice.fr expressed concerns that their specialised search engines were being intentionally given low rankings in query results, according to Holtz.
Ciao! was described as a longtime user of Google's AdSense ad-serving platform that began complaining about the standard terms of the arrangement after the company was bought by rival Microsoft in 2008.
Explore further: LinkedIn membership hits 300 million