The European Commission said on Tuesday it had launched an antitrust probe into allegations that Google had abused a dominant position in online search market.

The investigation would be centered on whether Google lowered the ranking of unpaid search results of competing services, which are specialized in providing users with specific online content such as price comparisons and by according preferential placement to the results of its own vertical search services in order to shut out competing services.

The European Union's (EU) antitrust watchdog said it would also look into allegations that Google imposed exclusivity obligations on advertising partners, preventing them from placing certain types of competing ads on their web sites, as well as on computer and software vendors, with the aim of shutting out competing search tools.

The opening of formal proceedings followed complaints by search service providers about unfavorable treatment of their services in Google's unpaid and sponsored search results coupled with an alleged preferential placement of Google's own services.

But the commission said the initiation of proceedings did not imply that it had proof of any infringements.

"It only signifies that the commission will conduct an in-depth investigation of the case as a matter of priority," it said.