The protests started in the morning near the university plaza subway station with as many as 20,000 students participating, according to a television news reporter for local station TVE interviewed in front of the Fira. He said there was some violence in the morning after some people in the crowd set a car on fire.
Students later walked to the Fira and sat in the traffic circle, blocking a main city street. The Mobile World Congress is the world's largest gathering of cellular operators and vendors, attracting about 60,000 attendees.
Students sat in the traffic circle about two hours. In response police set up road blocks, closed the front entrance of the Fira and the nearby subway station.
Many of the protesters left the site about 5:30 pm local time to protest in front of a local court building. One protester said about 20 students had been arrested as part of the otherwise peaceful protest in front of the Fira. There were no immediate reports of injuries.
Separately, a small group of educators held a separate protest on a side street with grade-school students (bottom).
The scene outside the Fira at about 5 pm local time as several hundred students stage a peaceful protest sitting in the traffic circle outside the exhibit center.
Grade-school children participated in a separate protest on a side street in the early evening.