Supporters of Catalonia’s independence vote launched sit-ins on Friday at schools where polling is due to take place, as police began moving in for an operation to shut down Sunday’s banned referendum.

Amid anger at what many perceive to be a heavy-handed crackdown by Spanish authorities, numerous groups have rallied to the cause.

Barcelona firefighters have vowed to protect the vote, while a column of tractors rolled into the city on Friday to begin guarding polling centres.