Sporting fans celebrating their club being crowned Portuguese champions for the first time in nearly two decades clashed with riot police in the early hours of Wednesday.
Fans had gathered on Tuesday evening outside the Sporting stadium in Lisbon where their team beat Boavista 1-0, jumping with happiness, hugging, waving flags and shouting "Champions" as hundreds of cars beeped their horns in celebration.
Sporting, who are still unbeaten with two games left, have 82 points after 32 matches, an unassailable eight-point advantage over second-placed Porto.
Soon after the match, fans spread across the city and thousands gathered in Lisbon's main square, Marques do Pombal, one of the stops where Sporting players paraded the trophy on an open-top bus.
Some broke down metal barriers put in place to keep them from getting too close to the bus, prompting riot police to fire rubber bullets and use batons to disperse the crowd.
Ambulances rushed to the square to help several fans who were injured.
Some fans threw glass bottles and smoke bombs towards police officers and journalists.
No fans were allowed to enter the stadium due to COVID-19 restrictions. Outside the stadium and around Lisbon some supporters ditched face masks, while maintaining social-distancing became close to impossible as more people showed up.
Police had warned fans not to gather in large groups and urged them to practice social distancing and wear a mask at all times, with spokesman Domingos Antunes saying he hoped the celebration would not turn into a "nightmare."
Although the title celebrations ended with clashes, some younger fans amongst the huge gathering outside the stadium on Tuesday evening had an unforgettable night: the first time they experienced their club winning the title.
"It is an incredible happiness that cannot be explained," overjoyed 20-year-old Diogo Carregosa told Reuters. "I waited a long time for this moment."
Nayara, a 24-year-old Sporting fan, teared up as she said: "Sporting won the championship in the year I started school and today, when I finish my studies, Sporting are champions again ... 19 years is a long time. It is a dream."
Sporting's relentless campaign was hard to envisage when they finished fourth last season, 22 points behind champions Porto, and were struggling to fill the hole left after talismanic captain Bruno Fernandes joined Manchester United.
The title win completed a huge turnaround in fortunes for the club three years after the squad was attacked by angry fans at the training ground.