By Jessica Corbett

German police deployed a water cannon and pepper spray to disperse around 500 protesters in Hamburg, ahead of the Group of 20 (G20) Summit this weekend, where advocacy groups say global leaders will continue to support a flawed model for creating a more just world.

Some activists gathered to march on a main street of the port city just before midnight on Tuesday, while hundreds had pitched tents along the Elbe river. Tuesday’s events follow weekend demonstrations that brought at least 10,000 peaceful protesters to Hamburg’s streets and waterways. Tens of thousands more anti-globalization protesters are expected to flood Hamburg over the weekend, as the summit kicks off.

Friday, representatives of the world’s 20 largest economies—19 countries and the European Union—will meet in Hamburg for the two-day summit hosted by German Chancellor Angela Merkel. Attendees will include U.S. President Donald Trump, Russian President Vladimir Putin, and Turkish President Recep Tayyip Erdoğan.

At least 30 groups have registered to demonstrate in Hamburg this week, organizing to challenge the G20’s agenda and the policies touted by nationalists like Trump and Putin, and the liberal European leaders alike.