"Thirty people were injured, three of them members of the police forces," Paris chief of police Bernard Boucault told a news conference. "Twenty-one people were also arrested for questioning after throwing projectiles or causing damage."
Boucault said "hundreds, maybe thousands of troublemakers" spoiled the celebrations, adding "we did not underestimate the means needed to tackle such a situation. Some 800 police officers were called up". He said nobody had been seriously hurt.
Some of those involved wore PSG shirts and climbed on to temporary scaffolding as the soccer club's players were showing off the French champions' trophy.
"The scaffolding is going to collapse. We can't welcome the players in these conditions," the ceremony's public announcer said as the players were forced to leave the Place du Trocadero earlier than expected.
Riot police fired tear gas to try to disperse the crowd after up to what police estimated was 15,000 people had gathered to celebrate PSG's first league title since 1994.
Bus shelters were destroyed during the episode with some of the people involved covering their faces.
A PSG players' cruise on the Seine river, which was part of the scheduled celebrations, was cancelled, the club said on its website (www.psg.fr).
"There will be no more celebrations on the streets of Paris for PSG," Boucault said.
PSG should be able to properly celebrate the title on Saturday when they host Stade Brest at the Parc des Princes, where the players spent most of the evening after the celebrations were ended.