BARCELONA (Reuters) - Thousands gathered in Barcelona on Thursday to mark the first anniversary of a police raid on Catalan government offices in the Mediterranean city, a move that sparked a huge demonstration ahead of a banned vote on a split from Spain.

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Streets in downtown Barcelona were filled with banners showing pro-independence jailed politicians and civil right activists.

The raid and subsequent protests stoked a febrile atmosphere that saw Spanish police wielding batons and firing rubber bullets at crowds attempting to vote in the referendum on Oct. 1 - images that flashed around the world.

During the Sept. 20 protests, Spanish police were trapped inside a Barcelona building and their vehicles were destroyed as anger among those favouring independence boiled over.

The Spanish police were trying to halt the referendum.

The rally was attended by current regional leader, Quim Torra, and Catalan parliament speaker, Roger Torrent.

Both demanded the release of some jailed Catalan leaders and to push ahead with the independence drive.

People chanted pro-independence slogans in Catalan, shouting: “Llibertat presos politics” (“freedom for political prisoners”).

After the vote on Oct. 1, Catalonia made a declaration of independence that led to Madrid taking over the regional administration.

Since then, pro-independence forces have returned to power in the regional parliament. Polls show those wanting secession and those preferring to stay part of Spain roughly evenly split, leading to a deep divide in Catalan society.