BERLIN - The European Union (EU) competition is investigating whether a taxation agreement signed between the German carmaker Volkswagen and Luxemburg breaches the bloc's strict competition rules, German media reported on Wednesday.

The reports cited information obtained by "Bloomberg" that competition authorities at the European Commission were assessing whether the Wolfsburg-based firm currently benefited from a tailored agreement with the low-tax destination Luxemburg which was not permissible under antitrust regulations.

Neither the finance ministry of Luxemburg nor Volkswagen have responded to the reports.

The preliminary query filed by the Commission is part of a wider offensive against so-called "sweetheart" tax deals which has embroiled several major corporations.

As a consequence, the likes of AbInbev, Fiat Chrysler and Starbucks have already been ordered to pay back taxes worth millions of euros to national tax authorities.