A CNN en Español team on the ground witnessed police using water cannons and tear gas to disperse the crowd, while protesters were seen hurling objects back at police.
A car belonging to a TV station was overturned and set on fire before it was extinguished by firefighters.
So far, there are no official reports of injuries, but CNNEE journalists witnessed paramedics helping injured people.
Demonstrators from various social groups and unions had gathered there to voice their opposition to the proposed reforms.
The bill – which has already been approved in the Chamber of Deputies – includes a declaration of a “public emergency in administrative, economic, financial and energy matters for a period of one year,” which would delegate legislative powers in those areas to the Executive Branch without having to go through Congress.
