Before the clashes erupted, elated fans outside the Sporting stadium in Lisbon, where their team beat Boavista 1-0, jumped with happiness, hugged, waved flags and shouted "Champions!" as hundreds of cars beeped their horns in celebration.
Some of the fans broke down metal barriers in place to keep them from getting too close to the Sporting players' open-top bus, leading riot police officers to fire rubber bullets to disperse the crowd.
Ambulances rushed to the square to help several injured people. Some fans spent hours throwing empty glass bottles and smoke bombs towards officers and journalists.