(Bloomberg) — At least 100 people have been arrested after far-right protests descended into rioting this weekend in England and Northern Ireland, with police warning that the violence may not be over.

Disturbances have broken out in towns and cities including Blackpool, Belfast and Bristol since Friday night, with a number of police officers attacked and injured. The riots represent one of the biggest challenges facing the month-old Labour government, as it struggles to rein in the unrest.