Thousands of students joined farmers and state workers in the Colombian capital Bogota to protest as the 11-day agricultural strike grows ever more violent.
Police fired water canon and tear gas as protesters hurled rocks, blocked roads and looted shops.
The strike is over new trade laws, which the farmers say have left them impoverished.
One protester explained why the students had taken to the streets:
“We support the farmers, but also we have our own issues, we demand free and good quality education.”
President Juan Manuel Santos flew over the city to witness the clashes as his government faces a growing number of difficulties, including tough peace negotiations with the FARC rebel group.
Colombian Defence Minister Juan Carlos Pinzon condemned the violence:
“Three police officers have gunshot wounds. Let it be clear these protesters are not doves. They are criminal gangs and members of FARC.”
The strike has united potato growers, dairy farmers and teachers.
Protests have also been reported in Cali and Medellin.