SPAIN was heading for another diplomatic tussle with Belgium last night after the Belgian defence minister tweeted his support for Catalan political prisoners who are on hunger strike.

Sander Loones’ wrote on Twitter: “Locked up for more than a year without being convicted. The Spanish Court does not even try its process to prevent the Court of Human Rights from ruling. Now, they are forced to make a hunger strike.

“No democrat should not shut up about it.”

An angry Josep Borrell, Spain’s foreign minister, told journalists as he arrived in Brussels for a meeting with his counterparts, the comments were unacceptable.

“The Belgian minister of defence has made statements that we consider unacceptable and will be answered,” he said.

This is the second time Borrell has clashed with Flemish politicians. Last month he withdrew the diplomatic credentials of the Flemish delegation to Spain after their parliament’s speaker, Jan Peumans, criticised the continued imprisonment of the Catalan pro-independence figures and Spanish democracy.

The row came as details were revealed of a series of orchestrated “public fasting” protests across Catalonia in support of Jordi Sanchez, Jordi Turull, Joaquim Forn and Josep Rull, who are refusing food at Lledoners prison, north of Barcelona.

Sanchez and Turull began their hunger strike on Saturday, while Forn and Rull joined them yesterday, in protest at the Constitutional Court’s delay in processing their cases for the European Court of Human Rights.

Forn’s sister Marta told The National the family was “very sad and angry” that it had come to this, but added: “It’s his decision.”

Details of the planned protests were still being worked out last night, but they will be held in the abbey at Montserrat, Cornella and the Catalan capital Barcelona. Organisers have not ruled out a fasting tomorrow – Constitution Day in Catalonia – which marks the anniversary of the 1978 referendum that led to a new constitution being approved.

Everyone who takes part will stop taking food for between a minimum of two and maximum of seven days.

Grassroots groups the Catalan National Assembly (ANC) and Omnium Cultural, are organising the protests, along with the parliamentary group Together for Catalonia (JxCat) and political parties the ERC, PDeCAT and CUP.

The detentions have been condemned by the International Association of Democratic Lawyers (IADL), which has called for the prisoners’ immediate release and for the arrest warrants issued against other – now exiled – politicians, to be revoked.

The hunger strikes – vagadefam – have been trending on Twitter, with user Joe Brew, saying: “The impact of the Catalan political prisoners’ hunger strike on international attention (measured via English language tweets): 1 week ago: ‘hunger strike’ appeared on twitter once every 120 seconds; today: 15 times per minute … That’s 3000% above baseline.”

Those refusing food appeared to be in good spirits, with Rull tweeting: “Thanks for the support and solidarity, because without them nothing would be possible.”

And supporters of St Andrews academic Professor Clara Ponsati tweeted: “The students of St Andrews stand in solidarity with all the Catalan political prisoners currently on hunger strike. This shouldn’t be necessary, but Spain continues to violate their rights.”