Spain's Ministry of the Interior is said to have hired up to three ropax vessels to accommodate national police and civil guard units, including riot police, mobilised to Catalonia to reinforce local forces.

Spanish media name the vessels as the 2,448-passenger cruise ferry Rhapsody (built 1996), 2,180-passenger GNV Azzura (built1980) and 1,650-passenger ferry Moby Dada (built 1981).

The former duo are owned by Grand Navi Veloci (GNV) of Genoa, while the Moby Dada is operated by Italian compatriot Moby Lines.

The Rhapsody and Moby Dada are now berthed at Barcelona and the GNV Azzura in Tarragona to the south. It is understood they will remain there until around 5 October.

The Moby Dada was earlier said to have been refused entry to the port of Palamos to the north of Barcelona.

The option to use passenger vessels is understood to have been taken to overcome the lack of hotel accommodation and to avoid potential friction between security personnel and the public.

All security forces’ leave has been temporarily suspended as part of Madrid’s efforts to stop an independence referendum being held in Catalonia on 1 October (dubbed “1-O”).

The referendum has been declared illegal by Spain’s constitutional court, while arrests of Catalan officials have sparked widespread protests.

Some 4,000 security personnel could be mobilized to the region to ensure the law is upheld.

The Barcelona Ports Stevedores Assembly voted today that its members will not supply the Rhapsody “in defence of civil rights”, while urging the central and Catalan governments to reopen a dialogue to resolve tensions peaceably.

The majority of dock workers in the port of Tarragona have taken the same position, according to reports.