Tens of thousands of people marched Saturday in Essen, Germany against an ongoing convention by the far-right Alternative for Germany party (AfD).

The protest was reported to be generally calm and violence-free, although several arrests were made and police said two officers were hospitalized after clashing with protestors. The A25 highway was also temporarily blocked. In response to the protests, the mayor of Essen Thomas Kufen emphasized that a clearer framework for a party’s selection of a host city for its convention must be established.

The AfD won a legal battle more than two weeks ago about an administrative contract between the Essen municipality and the venue-offering entity, which was to condition the public facility’s usage with a declaration by the AfD to not make any criminal statements. Since the AfD has not been declared as unconstitutional by the federal constitutional court, it was decided that this condition should be strictly assessed.

The Alternative for Germany came second in the last European Parliament Elections with about 15.90% of the votes, right after the Christian Democratic Union, which got around 30%. It first entered the German Parliament in 2017, placing third in that year’s elections, rising in popularity ever since. There have been previous demands to ban the AfD, and its opponents say they are a threat to Germany’s democracy. The German Federal Youth Association has previously stated that the AfD should be banned to confront fascism in Germany.