Buses and cars have been set on fire in Rio de Janeiro's city centre. Road blocks set up by activists were also ablaze and shops were vandalised.
For most of the day the strike had been largely peaceful. Many people stayed at home and shops, schools and banks remained closed across the country.
Unions called the strike in protest at proposed pension reforms.
President Michel Temer said he regretted the incidents in Rio. But he stressed that he would continue his "efforts to modernise the country".
