Thousands of protesters gathered in Erfurt on Saturday to oppose Germany’s far-right Alternative for Germany (AfD), blocking roads leading to the party’s annual conference and causing major disruptions.

Reuters reports that the demonstrations involved supporters from unions, civil society groups, and left-wing parties, while large numbers of police—reinforced from across Germany—were deployed in riot gear ahead of the event. Protesters sat in rows to block highways and access routes to the convention centre where the conference was held.

Police estimated around 15,000 people joined demonstrations in and around Erfurt.

The AfD began its two-day conference by re-electing its co-leaders Alice Weidel and Tino Chrupalla, leaders who have overseen the party’s rise as it tops national opinion polls. In opening remarks, AfD speakers mocked the protesters as anti-democratic and portrayed AfD’s growth as a response to Germany’s decline.

The Reuters report also places the conference ahead of elections in Germany’s eastern states of Saxony-Anhalt and Mecklenburg-Vorpommern, which AfD hopes could pave the way for stronger national influence—an outcome that opponents say has alarmed them. A spokesperson for the anti-AfD umbrella group Widersetzen said demonstrators intended to make clear they would “simply won’t tolerate” the party’s rise.