At least 13 people were killed and more than 50 injured after a van rammed through crowds of people in the heart of Barcelona Thursday in what police described as a terror attack.

Eyewitnesses reported scenes of panic and chaos as the van plowed through crowds in the renowned Las Ramblas avenue, which was teeming at the time with locals and tourists. One person has been arrested, Catalan police said. Police were treating the incident as an act of terrorism and sealed off the area.