A court in Spain on Thursday banned Catalonia's president Quim Torra from holding public office for 18 months after finding him guilty of disobedience for failing to remove separatist symbols from public buildings during an election campaign.

Torra swiftly said he would appeal the ruling, which will only come into effect if it is confirmed by Spain's Supreme Court, a decision that could take months.

If confirmed, the ruling could trigger a fresh political crisis in Catalonia possibly leading to an early election in the wealthy northeastern region.

"It is not a politically motivated court that will remove me from office. Only the Catalan parliament can do that," Torra said after the court issued its ruling.

In March, Spanish electoral authorities ordered Torra to remove separatist symbols to respect institutional neutrality ahead of parliamentary elections in April.

They objected in particular to a banner outside the Catalonian regional government headquarters that read "Freedom for political prisoners and exiles" next to a yellow ribbon indicating support for nine detained Catalan separatist leaders who were sentenced in October to lengthy jail terms over an abortive 2017 independence bid.

That court ruling set off a wave of angry protests in Barcelona and other Catalan cities that repeatedly descended into violence. The Catalan government ignored two deadlines to take the banner down before finally ceding just before a planned police intervention.

Catalonia's High Court of Justice ruled that Torra had displayed a "forceful, repeated and stubborn resistance" to follow the orders of the electoral board which "had been dictated in accordance with the law".