Scotland is at the centre of diplomatic spat as Catalonia's foreign minister prepares to make an "official" visit to Edinburgh that Spain insists is unauthorised.

Catalan envoy Raul Romeva will fly to Scotland later this month to meet senior SNP figures in what Madrid sees as a clear challenge to its control over international affairs.

Spanish authorities do not recognise Mr Romeva - a veteran campaigner for Catalonia's independence - as his country's foreign minister.

They believe that as an official in what they see as a mere "regional" administration, he should clear any international meetings with them.

Read More: "I am a Basque." Alex Salmond returns to Iberian politics

So Mr Romeva's scheduled April 28 visit to Scotland has sparked headlines warning of serious diplomatic consequences for Scotland - especially if the Catalan minister meets his Scottish counterpart, Fiona Hyslop.

In what was seen in Edinbugh as a veiled threat, Madrid daily ABC reported: "The Scottish Government is aware that a meeting between Ms Hyslop and Mr Romeva could provoke discomfort in the Spanish Embassy and a protest to the Foreign office."

The paper, which is close to the caretaker Conservative government of Mariano Rajoy, stressed that Mr Romeva had not informed the Spanish Foreign Ministry about his trip.

Background: Spain's government still interim four months after inconclusive general election

Concern about an official reception for Mr Romeva comes despite the fact that Scottish ministers are too busy fighting for their seats in Holyrood elections to meet foreign dignitaries.

However, senior party figures will meet Mr Romeva, a former MEP with Catalan Greens, Iniciativa per Catalunya Verds

SNP MEP Alyn Smith, pictured below, said: "I would think a meeting with any of our Ministers would be unlikely as we are all busy campaigning for re-election, but I certainly will be meeting Raul as we were good colleagues in the European Parliament for ten years and we have much to talk about.

"If this provokes discomfort in Madrid perhaps our Spanish friends might wish to reflect on the discomfort we felt at the intemperate, ill advised and wrong remarks of their Prime Minster during our referendum."

HeraldScotland: Alyn Smith. (44139721)

Spanish unionists - who have blocked a Scottish-style independence referendum in Catalonia - have been openly hostile to the SNP and its government.

The SNP - which, as ABC reported has traditionally been "cautious" about criticising Spain - has become increasingly close to Catalonia's independence movement in recent months.

Read More: "I am a Basque." Alex Salmond returns to Iberian politics

A broad alliance of pro-independence parties, including Mr Romeva's Esquerra, last year won a general election mooted as a kind of proxy independence referendum.

A new "transitional" government under President Carles Puigdemont, pictured, is now working to a road map for independence - despite Spain's legal resistance.

HeraldScotland:

This has included the creation of a Foreign Ministry, led by Mr Romeva and regarded by Madrid as unconstitutional in one of the key legal clashes between the two Iberian nations.

Spain's constitutional court in February suspended the Catalan Government decree creating the foreign ministry. The Catalans changed the name of the ministry in an attempt to side-swerve the legal action.

However, Mr Romeva on his Twitter account still calls himself, in English, "Minister of Foreign Affairs, Institutional Relations and Transparency, Catalan Government".

Background: UK government caught lobbying Spanish press against Scottish independence.

Mr Romeva also intends to visit London later this month and has scheduled a meeting with a Eurosceptic Tory MP, Andrew Rosindell, who has championed the cause of continued British control of Gibraltar. That encounter, sources stress, is also not going to please Madrid's foreign ministry.

Read More: "I am a Basque." Alex Salmond returns to Iberian politics