"These radical activists and weaponized NGOs have advanced censorship crackdowns by foreign states -- in each case targeting American speakers and American companies," the State Department said in a statement announcing the sanctions.

The measure targeted Thierry Breton, the former top tech regulator at the European Commission, who often clashed with tech tycoons such as Elon Musk over their obligations to follow EU rules.

Breton was described by the State Department as the "mastermind" of the EU's Digital Services Act (DSA), a major piece of legislation that imposes content moderation and other standards on major social media platforms.

The DSA has become a bitter rallying point for US conservatives who see it as a weapon of censorship against right-wing thought in Europe and beyond, an accusation the EU furiously denies.

The DSA stipulates that major platforms must explain content-moderation decisions, provide transparency for users and ensure researchers can carry out essential work, such as understanding how much children are exposed to dangerous content.

- 'Extraterritorial overreach' -

The US government has scaled up its attacks on EU regulations after Brussels earlier this month fined Musk's X for violating DSA rules on transparency in advertising and its methods for ensuring users were verified and actual people.

Last week the US government signaled that key European businesses could be targeted in response, listing Accenture, DHL, Mistral, Siemens and Spotify among others.

The visa ban also targeted Imran Ahmed of the Center for Countering Digital Hate (CCDH), a nonprofit that fights online hate, misinformation, and disinformation that also fell in the crosshairs of Musk after his takeover of Twitter, later renamed X.

Also subject to the ban were Anna-Lena von Hodenberg and Josephine Ballon of HateAid, a German organization that the State Department said functions as a trusted flagger for enforcing the DSA.

Clare Melford, who leads the UK-based Global Disinformation Index (GDI), rounded out the group.

Washington is also attacking the UK's Online Safety Act, Britain's equivalent of the DSA that seeks to impose content moderation requirements on major social media platforms.

The White House last week suspended implementation of a tech cooperation deal with Britain, saying it was in opposition to the UK's tech rules.

"President Trump has been clear that his America First foreign policy rejects violations of American sovereignty," Secretary of State Marco Rubio said in a statement.

"Extraterritorial overreach by foreign censors targeting American speech is no exception," he added.