Mass demonstrations in Germany that passed largely peacefully on Saturday erupted in violence as night fell and rioters faced off against police in Frankfurt, Cologne, Hamburg and Berlin.

Authorities blocked off Frankfurt’s main shopping street Die Zeil and arrested more than 30 people after demonstrators smashed shop windows and made off with streetwear and other goods. Officers arrested one person suspected of breaking into a gun store and stealing two weapons, which were retrieved.

Police used water cannons to break up the crowds as protestors threw Molotov cocktails and set off fireworks. By early Sunday, the streets had emptied, while police maintained a visible presence.