Facebook has been ordered to stop collecting and storing data on WhatsApp users in Germany, marking the first regulatory challenge to a controversial data-sharing scheme that the social media company announced in August. In a statement published Tuesday, Germany's privacy watchdog said that sharing WhatsApp user data with Facebook, the messaging app's parent company, constitutes "an infringement of national data protection law." The regulatory body also ordered Facebook to delete all data that has already been transferred from WhatsApp.

Facebook's data-sharing scheme has been closely monitored by privacy groups across Europe. When Facebook acquired WhatsApp in 2014, the app's co-founder, Jan Koum, assured users that their privacy would not be compromised.