SPAIN has continued its heavy-handed bid to crack down on the Catalan Government’s plans to hold an independence referendum on October 1 and – in a move that has further increased tensions in the state – Spanish Prime Minister Mariano Rajoy is sending hundreds of police reinforcements to Catalonia.

Three ferries capable of carrying more than 6000 people have been brought in to accommodate the extra officers.

Spain’s Interior Ministry said they would provide support for Catalan regional officers, who have – along with the Guardia Civil – been ordered to stop the referendum going ahead.

READ MORE: Spain's actions signal 'a return to the fall of democracy' as crackdown on Catalonia continues

However, dockers in Barcelona’s port have voted to refuse to supply the ships that are docked there.

In a statement on social media, dockworkers’ representatives labelled them “repression ships” and said the decision not to supply them was taken “to defend civil rights”.

Catalan sources say two of the ships – the Moby Dada and the Rhapsody – have berthed in the Catalan capital Barcelona, while the third, GNV Azzurro has docked in Tarragona, around 60 miles south of the city.

They added that the vessels are cleared to stay until October 5, four days after the poll, and other than being used to accommodate Spanish police officers, no further details have been given about their purpose.

More than 50 trade union groups across Catalonia are also understood to have been involved in discussions about staging a general strike because of the actions of the central government in Madrid.

A Catalan regional judge, meanwhile, has released the remaining six people who were among 15 arrested on Wednesday in a crackdown on referendum preparations. A statement said they had declined to give evidence.

The six are still being investigated for alleged disobedience, abuse of power and misappropriation of funds – all in connection with the planned ballot – and have been ordered to appear before the court on a weekly basis. Former secretary general of the economy ministry, Josep Maria Jové, was the highest-ranking official to be charged.

A prosecutor at the Spanish high court has filed a sedition lawsuit calling for an investigation to identify the organisers of street protests that involved tens of thousands of demonstrators in Barcelona on Wednesday.

The official claimed the protests aimed to “forcibly prevent” security forces carrying out their duties, making those responsible guilty of actions that impede the application of the law “through force or by illegal means”. The crime of sedition, which falls under the jurisdiction of Spain’s special high court, the Audiencia Nacional, carries jail sentences of between four and 15 years.

Spontaneous protests involving tens of thousands of people began after Spanish civil guards raided more than 40 Catalan Government buildings and arrested officials said to be involved with the referendum.

The allegations relate to unidentified individuals blocking roads outside the targeted buildings, puncturing police car tyres, “to impede the legitimate performance of their duties”.

Also mentioned in the accusations is the setting up by the Catalan National Assembly (ANC) of a meeting point for volunteers, and the head of the Catalan cultural society Òmnium Cultural, Jordi Cuixart, calling for “permanent mobilisation”.

The lawsuit said the “ultimate aim” of the demonstrations was “the holding of a referendum to bring about the proclamation of an independent Catalan republic”. The prosecutor acknowledged that the aim was only criminal if achieved through a “public and riotous uprising”.