Overseas supporters of President Trump disrupted a speech on Saturday by London Mayor Sadiq Khan, a day after the outspoken Trump critic said the president had “got the message” that he is not welcome in the United Kingdom.

Khan was forced to pause his remarks at a Fabian Society conference in London after a group of protesters from the far-right White Pendragons group began yelling for the mayor to be arrested, while waiving American flags.

“Ladies and gentlemen, we’re here today to make a non-violent, peaceful citizen’s arrest,” shouted one of the protesters, according to local media.

Khan has repeatedly urged British Prime Minister Theresa May to disinvite Trump from visiting the U.K., citing the president’s controversial comments about Muslim immigrants as evidence that he doesn’t share the same values as America’s closest ally.

Both May and Khan condemned Trump last fall after he retweeted a series of anti-Muslim videos that had originally been shared by Jayda Fransen, the deputy leader of a far-right British political group.

The London mayor took a dig at his hecklers on Saturday after security began escorting them out, suggesting he had been disrupted by a group of “very stable geniuses” – a reference to how Trump described himself in a series of tweets last week.

White House officials confirmed on Friday that Trump will not attend the opening of the new U.S. embassy in south London.

"Reason I canceled my trip to London is that I am not a big fan of the Obama Administration having sold perhaps the best located and finest embassy in London for ‘peanuts,’ only to build a new one in an off location for 1.2 billion dollars," Trump later tweeted.