LONDON — Two leaders of a British far-right group that gained publicity when it was retweeted by President Trump have been arrested for allegedly stirring up hatred.

Britain First leader Paul Golding and his deputy Jayda Fransen were detained in Belfast after attending a court hearing for Fransen. She’s charged with hate speech during a ‘‘Northern Ireland Against Terrorism’’ rally in Belfast in August. Golding was arrested Thursday over the same rally, and Fransen was detained over a social media post criticizing Islam. Last month Trump retweeted videos from Fransen’s account purporting to show violence by Muslims. Britain First opposes multiculturalism and what it calls the ‘‘Islamization’’ of Britain.