Germany's competition regulator said Friday it was expanding an antitrust investigation into Google and its parent company Alphabet to include Google News Showcase, a new service the US tech giant provides to media publishers.

The Federal Cartel Office will examine whether the Google service, which was launched in Germany last autumn and allows publishers to place journalistic content more prominently online, is compatible with German competition law.

It is the latest in a string of probes that the watchdog has opened this year under a new law allowing it to further scrutinise US tech giants such as Google, Amazon and Facebook.

While cooperation with Google could be "an attractive option" for publishers and other news providers, it should not "result in discrimination between individual publishers", said the regulator's president Andreas Mundt in a statement.

"Google's strong position in providing access to end-customers must not lead to a situation where competing services offered by publishers or other news providers are squeezed out of the market."

Launched in response to a complaint by German-based company Corint Media, the probe will notably assess whether Google has given itself an unfair advantage over rival services by integrating News Showcase into its general search function.

The investigation will be part of a wider probe into Google which the German watchdog announced last week. 

It follows announcements of similar probes into Amazon and Facebook since an amendment to Germany's competition law was passed in January.

Last month, the watchdog said it now has more power to "intervene earlier and more effectively" against big tech companies, rather than simply punishing them for abuses of their dominant market position.