COPENHAGEN, Denmark (AP) — Police in Denmark say that 25 people have been detained for allegedly taking part in clashes during a March protest marking the 10th anniversary of a squatter eviction that sparked riots in Copenhagen.

Police spokesman Mikael Wern said that 10 locations were raided early Wednesday and officers found caltrops — spikes used to deflate vehicle tires — gas masks and objects that could be thrown.

Wern said a handful of the 1,000 participants in the March 1 protest threw rocks, fireworks and bottles at riot police. No one was reported injured, but dozens of shop windows were smashed.

Riots broke out on March 1, 2007, after squatters were evicted from an abandoned building in Copenhagen that had been a center for young leftists and punk rockers for nearly three decades.