Barcelona is preparing for a fifth day of protesting after the conviction of 12 independence leaders.
Far-right anti-independence activists clashed with police in the Catalan Capital late on Thursday as protestors attempt to storm a separatist protest.
Health authorities in the region have reported some 18 people injured with 11 protesters arrested by regional police.
Spainish central authorities have reported flight disruption and have said that 46 flights to and from the region have been cancelled on Friday due to strike action from pro-independence unions.
Picketers have blocked the border with France at the point of La Jonquera. Further mass protests are expected to gather in Barcelona city centre on Friday afternoon. Five marches of tens of thousands of people from inland towns are expected to participate in the mass protest with striking students and workers.
Those who have booked travel to Barcelona are advised to check the status of their flights before travel and to contact their local travel agent for further information. Travellers already in Barcelona should remain vigilant and stay clear of areas of protest.
