Microsoft's antitrust battles against Google in Europe accelerated this week with a report claiming that the software giant had lodged yet another complaint against its online competitor. This new complaint allegedly centers on Google's copycat social networking service, Google+.

The complaint was first reported by Reuters, which cites two sources familiar with the action.

Details are thin, however, with the sources noting the "sensitivity" of the complaint, which is the second such antitrust abuse allegation from Microsoft and against Google in the past week. See Microsoft Lodges EU Antitrust Complaint Against Google, Motorola Mobility for more information about last week's complaint.

And Microsoft is apparently not the only company involved in the complaint. The Reuters report doesn't name other parties.

Google+ is Google's quickly growing social networking service, and it appears to be an amalgamation of Facebook and Twitter features. Google is often criticized for simply copying its competitors' products, and Google+ is arguably the best example of that charge.

Not coincidentally, this isn't even the first antitrust investigation to involve the service: The US Federal Trade Commission (FTC) expanded a prior investigation of Google to include Google+ last month.

European Commission (EC) regulators and Microsoft both declined to comment on the complaint.