Protesters clashed with police in the Spanish region of Catalonia on Wednesday, with some setting cars ablaze on the third day of disturbances caused by convictions handed down to leaders of a failed bid to declare an independent state.

Divisions over the secession drive that roiled Spain in 2017 have re-surfaced on the streets of the region's main city Barcelona since the Supreme Court sentenced nine politicians and activists to up to 13 years in jail.

Despite calls for calm from the regional government, protesters blocked roads and train lines during the day and, after dark, set fire to cars. The regional Mossos police force said acid had been thrown at officers.