LONDON — European authorities blamed Russian groups on Friday for disinformation campaigns designed to depress turnout and sway public opinion in last month’s European Union elections, an official accounting that underscored how Russian interference has not abated and that Facebook and other tech platforms remain vulnerable to meddling.

The preliminary review by the European Commission and the bloc’s foreign policy and security arm found that Russian-linked groups and other nonstate actors had worked to undermine credibility in the European Union through Facebook, Twitter and YouTube. Officials said new regulations might be needed to force internet platforms to do more to stop the spread of deliberately false information.

“The evidence collected revealed a continued and sustained disinformation activity by Russian sources aiming to suppress turnout and influence voter preferences,” the report said.

The report was the first official substantiation by the European Commission of the role that Russians and other groups played in disinformation in the May elections, which many investigators, academics and advocacy groups had warned about. It was a reminder of how active Russians and others continue to be in spreading divisive content online to inflame and stoke electorates all over the world, a strategy that the Kremlin had pioneered in the 2016 American presidential election.