Thirteen people have suffered minor injuries after clashes broke out between police and protesters in Spain's Catalonia region on Monday, following the Spanish Supreme Court sentencing of pro-independence leaders.
Tense moments were experienced at Barcelona's El Prat airport in particular, where scores of people blocked access to the building and forced the cancellation of at least a hundred flights.
A later outbreak of violence at the airport left ten people injured, and a further three were injuried in action across other parts of the region.
The protests in Catalonia, especially in the big cities, are monitored by a strong security force, including both the Catalan regional police (Mossos d'Esquadra) and the state bodies (National Police and Guardia Civil), which sent 2,000 additional troops to the region to ensure public order.
The demonstrations in El Prat airport were organised by Tsunami Democratic, an organization that claims to be an independent grassroots movement, without any political back-up.
At 13.00 CET, the group posted instructions on social media to flood Barcelona's airport with people in order to halt its operations.
Later in the evening, Tsunami Democratic announced that 1,200 cars were headed to Madrid's Barajas Airport to carry out similar disruption.
Tsunami Democratic and other social media users have published videos of traffic jams in the vicinity of the airport, however, Madrid's Civil Protection department said there were no incidents in Barajas at that time.
It added that all citizens should use official accounts to stay informed.
Social media has also been flooded with videos claiming to show officers with Mossos d'Esquadra and the Spanish National Police beating some of the protesters.
Several journalists are among those say they have been attacked by members of the security forces while reporting on the demonstrations.
Meanwhile, around a hundred people invaded the railway near a train station in Gerona, temporarily interrupted the movement of conventional and high-speed trains between Barcelona and the French border.
Subsequently, some of the protesters also cut off traffic on the AP-7 motorway in Gerona. This is an important road that connects the French border with Barcelona. Fourteen other Catalan roads were cut off at different times of the day.