In a document filed with the National High Court in Madrid on Friday, accusing protestors in Barcelona on Wednesday of sedition, Spain's public prosecutor describes how National Police officers moved away from the headquarters of the party that supports the regional government in Catalonia, the CUP, later in the evening.

"At 8 p.m., the officers left the location, firing shots to avoid an imminent attack on a police van."

The prosecutor does not describe how many shots were fired, or what type of shots were fired.

A mobile phone video obtained by The Spain Report shows Spanish police vehicles moving away from the CUP building on Wednesday evening, surrounded by hundreds of protestors.

Two CUP sources confirmed independently that the images in the video appear to show the street their headquarters is located on in Barcelona, Calle Casp.

One officer behind the last van can be clearly seen firing two shots of some description as the crowd moves closer towards his vehicle. The crowd then moves suddenly away.

Spanish news agency Europa Press cited unnamed police sources on Friday describing the shots as "riot control ammunition, not live rounds".

The National Police declined to comment further. The Spanish Home Office was unavailable for comment on Friday evening.